soc: nordic: nrf92: Set PPR hart ID to processor ID

Booting VPRs requires changing the default value of CONFIG_RV_BOOT_HART.
This must be reverted (back to zero) for a future nRF9230 SoC revision,
which will align more closely with the RISC-V spec.

Signed-off-by: Grzegorz Swiderski <grzegorz.swiderski@nordicsemi.no>