KVM: arm64: nv: Apply RESx settings to sysreg reset values

KVM: arm64: nv: Apply RESx settings to sysreg reset values

While we have sanitisation in place for the guest sysregs, we lack
that sanitisation out of reset. So some of the fields could be
evaluated and not reflect their RESx status, which sounds like
a very bad idea.

Apply the RESx masks to the the sysreg file in two situations:

- when going via a reset of the sysregs

- after having computed the RESx masks

Having this separate reset phase from the actual reset handling is
a bit grotty, but we need to apply this after the ID registers are
final.

Tested-by: Joey Gouly <joey.gouly@arm.com>
Reviewed-by: Joey Gouly <joey.gouly@arm.com>
Link: https://lore.kernel.org/r/20250112165029.1181056-3-maz@kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>