[verilator] Investigate why verilator with sival_rom_ext fails on load access exception

### Description

When running verilator using the sival_rom_ext as defined in #22836:
```./bazelisk.sh run //sw/device/tests:edn_kat_sim_verilator_sival_rom_ext```
the ROM returns an error:
```BFV:05495202```
This is an interrupt error with (encoded) mcause: exception 5 (load access exception).

Investigate why this work on a real device but not in verilator.