[rom_ext] Boot Log does not report the correct primary_bl0_slot after a next_bl0_slot_req

### Description

I'm seeing this issue occur using the ROM_EXT 0.4 prodc prebuilt on the `earlgrey_es_sival` branch.

The primary boot slot field is not being reported correctly via the boot log for the boot cycle where the ROM_EXT handles the boot service to switch the primary bl0 slot. Having the primary slot being correctly reported by ROM_EXT is useful to know if an image update was successful or not.

How to reproduce the issue:

1. In each slot have two valid BL0 images. The primary slot is boot slot A, and the active slot is A as well.
2. Put the boot service request to change the primary slot to the inactive slot B with the following fields `next_bl0_slot=kBootSlotUnspecified` and `primary_bl0_slot=kBootSlotB`
4. Make a SW reset request through rstmgr peripheral
5. On bl0 re-entry the primary slot is swapped because the active slot is now B. However he boot log reports the primary slot as A still.

If I reboot the device again, the primary slot updates to the correct value, so it seems like some issue with the ROM_EXT not updating the boot_log correctly after the service request.