KVM: arm64: nv: Sanitise ICH_HCR_EL2 accesses

As ICH_HCR_EL2 is a VNCR accessor when runnintg NV, add some
sanitising to what gets written. Crucially, mark TDIR as RES0
if the HW doesn't support it (unlikely, but hey...), as well
as anything GICv4 related, since we only expose a GICv3 to the
uest.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20250225172930.1850838-8-maz@kernel.org


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