arm: properly handle RES0/1 for SCTLRs

arm: properly handle RES0/1 for SCTLRs

They were being treated as RAZ/RAO, which is incorrect.
Put the access masks in the register metadatabase now that we have one.

Also fix this for HVBAR.

Change-Id: I097c847e35be2d59fb8235fc621bb061ef514cfb
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/10401
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Maintainer: Giacomo Travaglini <giacomo.travaglini@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>