KVM: arm64: selftests: Sync ID_AA64MMFR3_EL1 in set_id_regs

When we added coverage for ID_AA64MMFR3_EL1 we didn't add it to the list
of registers we read in the guest, do so.

Fixes: 0b593ef1 ("KVM: arm64: selftests: Catch up set_id_regs with the kernel")
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20250818-kvm-arm64-selftests-mmfr3-idreg-v1-1-2f85114d0163@kernel.org


Signed-off-by: Oliver Upton <oliver.upton@linux.dev>