KVM: arm64: Handle AArch32 SPSR_{irq,abt,und,fiq} as RAZ/WI

When trapping accesses from a NV guest that tries to access
SPSR_{irq,abt,und,fiq}, make sure we handle them as RAZ/WI,
as if AArch32 wasn't implemented.

This involves a bit of repainting to make the visibility
handler more generic.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20231023095444.1587322-6-maz@kernel.org
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>