[rom_ext] BootLog incorrect for currently executing ROM_EXT slot

### Description

It appears that the boot log that reports the active ROM_EXT is incorrect in some scenarios. Notice the following from the abridge firmware log after performing a firmware update that contains both a new ROM_EXT and new Owner Firmware.

* `Starting ROM_EXT 0.2`
* `0x406007a8: 5f5f4141 00000000 00000002 00010000` (memory dump of BootLog section start with [`rom_ext_slot`](https://github.com/lowRISC/opentitan/blob/master/sw/device/silicon_creator/lib/boot_log.h#L33)
* `Starting ROM_EXT 0.3`
* `0x406007a8: 5f5f4141 00000000 00000003 00010000`
* This is especially concerning since the `rom_ext_slot` is reporting SlotA (`AA__`), but the version is reporting `0.3`, but SlotA contains 0.2, and SlotB contains 0.3. I am pretty sure 0.3 is what actually ran since it printed `Starting ROM_EXT 0.3` on the UART.

The boot log remains incorrect event after performing soft reboots from FW (via `reboot` console command). Only after I perform a chip reset with the `RESET_L` pin, do I see the boot log be correct.

Log from a ROM_EXT and owner firmware update:

```
Starting ROM_EXT 0.2
Warning: UDS certificate not valid.
0: 40130000 NAPOT L--- sz=00001000
1: 40480000 NAPOT L--- sz=00000400
2: a0010400 ----- ---- sz=00000000
3: a0071d0c TOR -X-R sz=0006190c
4: a0000000 NAPOT ---R sz=00080000
5: 00000000 ----- ---- sz=00000000
6: 00000000 ----- ---- sz=00000000
7: 00000000 ----- ---- sz=00000000
8: 00000000 ----- ---- sz=00000000
9: 00000000 ----- ---- sz=00000000
10: 20000400 ----- ---- sz=00000000
11: 20008a78 TOR -X-R sz=00008678
12: 20000000 NAPOT ---R sz=00100000
13: 00000000 ----- ---- sz=00000000
14: 40000000 NAPOT --WR sz=10000000
15: 10000000 NAPOT --WR sz=00020000
mseccfg = 00000002
entry: 0xa0010730

[ 0.001] Starting OpenTitan RO 0.0.2 RW 0.36.1
[ 0.001] DBG/ti50_common_tot:v0.0.1372-09498a29 libtock-rs:v0.0.925-1213708 tock:v0.0.9673-2649e0509 ms-tpm-20-ref:v0.0.318-9942b1f jettrink@rink.bld.corp.google.com 2024-07-01 10:20:26
> md 0x406007a8 16
md 0x406007a8 16
0x406007a8: 5f5f4141 00000000 00000002 00010000
0x406007b8: 00000000 00000000 5f5f4141 00000000
0x406007c8: 00000000 00000000 00000000 5f5f4141
0x406007d8: 00000000 00000000 00000000 00000000
>
[ 272.146] at 0x090000
[ 272.157] at 0x090400
...
[ 276.413] at 0x08a000
[ 276.422] at 0x08a400
[ 276.438] Erase on active bank.
[ 276.440] turn_update_on: rebooting in 100 ms
Starting ROM_EXT 0.3
Warning: UDS certificate not valid.
CDI_0 certificate not valid. Updating it ...
CDI_1 certificate not valid. Updating it ...
0: 40130000 NAPOT L--- sz=00001000
1: 40480000 NAPOT L--- sz=00000400
2: a0010400 ----- ---- sz=00000000
3: a0071d0c TOR -X-R sz=0006190c
4: a0000000 NAPOT ---R sz=00080000
5: 00000000 ----- ---- sz=00000000
6: 00000000 ----- ---- sz=00000000
7: 00000000 ----- ---- sz=00000000
8: 00000000 ----- ---- sz=00000000
9: 00000000 ----- ---- sz=00000000
10: 20080400 ----- ---- sz=00000000
11: 200889a4 TOR -X-R sz=000085a4
12: 20000000 NAPOT ---R sz=00100000
13: 00000000 ----- ---- sz=00000000
14: 40000000 NAPOT --WR sz=10000000
15: 10000000 NAPOT --WR sz=00020000
mseccfg = 00000002
entry: 0xa0010730

[ 0.000] Starting OpenTitan RO 0.0.2 RW 0.36.1
[ 0.000] DBG/ti50_common_tot:v0.0.1372-09498a29 libtock-rs:v0.0.925-1213708 tock:v0.0.9673-2649e0509 ms-tpm-20-ref:v0.0.318-9942b1f jettrink@rink.bld.corp.google.com 2024-07-01 10:20:26

> md 0x406007a8 16
md 0x406007a8 16
0x406007a8: 5f5f4141 00000000 00000003 00010000
0x406007b8: 00000000 00000000 5f5f4141 00000000
0x406007c8: 00000000 00000000 00000000 5f5f4141
0x406007d8: 00000000 00000000 00000000 00000000
```

Log from firmware initiated soft reboot

```
> reboot

Starting ROM_EXT 0.3
Warning: UDS certificate not valid.
0: 40130000 NAPOT L--- sz=00001000
1: 40480000 NAPOT L--- sz=00000400
2: a0010400 ----- ---- sz=00000000
3: a0071d0c TOR -X-R sz=0006190c
4: a0000000 NAPOT ---R sz=00080000
5: 00000000 ----- ---- sz=00000000
6: 00000000 ----- ---- sz=00000000
7: 00000000 ----- ---- sz=00000000
8: 00000000 ----- ---- sz=00000000
9: 00000000 ----- ---- sz=00000000
10: 20080400 ----- ---- sz=00000000
11: 200889a4 TOR -X-R sz=000085a4
12: 20000000 NAPOT ---R sz=00100000
13: 00000000 ----- ---- sz=00000000
14: 40000000 NAPOT --WR sz=10000000
15: 10000000 NAPOT --WR sz=00020000
mseccfg = 00000002
entry: 0xa0010730

[ 0.000] Starting OpenTitan RO 0.0.2 RW 0.36.1
[ 0.000] DBG/ti50_common_tot:v0.0.1372-09498a29 libtock-rs:v0.0.925-1213708 tock:v0.0.9673-2649e0509 ms-tpm-20-ref:v0.0.318-9942b1f jettrink@rink.bld.corp.google.com 2024-07-01 10:20:26

> md 0x406007a8 16
md 0x406007a8 16
0x406007a8: 5f5f4141 00000000 00000003 00010000
0x406007b8: 00000000 00000000 5f5f4141 00000000
0x406007c8: 00000000 00000000 00000000 5f5f4141
0x406007d8: 00000000 00000000 00000000 00000000
```

Log after performing `ott gpio apply RESET && ott gpio remove RESET`

```
Starting ROM_EXT 0.3
Warning: UDS certificate not valid.
0: 40130000 NAPOT L--- sz=00001000
1: 40480000 NAPOT L--- sz=00000400
2: a0010400 ----- ---- sz=00000000
3: a0071d0c TOR -X-R sz=0006190c
4: a0000000 NAPOT ---R sz=00080000
5: 00000000 ----- ---- sz=00000000
6: 00000000 ----- ---- sz=00000000
7: 00000000 ----- ---- sz=00000000
8: 00000000 ----- ---- sz=00000000
9: 00000000 ----- ---- sz=00000000
10: 20080400 ----- ---- sz=00000000
11: 200889a4 TOR -X-R sz=000085a4
12: 20000000 NAPOT ---R sz=00100000
13: 00000000 ----- ---- sz=00000000
14: 40000000 NAPOT --WR sz=10000000
15: 10000000 NAPOT --WR sz=00020000
mseccfg = 00000002
entry: 0xa0010730

[ 0.000] Starting OpenTitan RO 0.0.3 RW 0.36.1
[ 0.000] DBG/ti50_common_tot:v0.0.1372-09498a29 libtock-rs:v0.0.925-1213708 tock:v0.0.9673-2649e0509 ms-tpm-20-ref:v0.0.318-9942b1f jettrink@rink.bld.corp.google.com 2024-07-01 10:20:26
> md 0x406007a8 16
md 0x406007a8 16
0x406007a8: 42425f5f 00000000 00000003 00010000
0x406007b8: 00000000 00000000 5f5f4141 00000000
0x406007c8: 00000000 00000000 00000000 5f5f4141
0x406007d8: 00000000 00000000 00000000 00000000
```

Notice that `0x406007a8: 42425f5f 00000000 00000003 00010000` correct indicates that SlotB (`__BB`) is executing ROM_EXT version 0.3 now.