KVM: arm64: Enforce NV limits on a per-idregs basis

KVM: arm64: Enforce NV limits on a per-idregs basis

As we are about to change the way the idreg reset values are computed,
move all the NV limits into a function that initialises one register
at a time.

This will be most useful in the upcoming patches. We take this opportunity
to remove the NV_FTR() macro and rely on the generated names instead.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Joey Gouly <joey.gouly@arm.com>
Link: https://lore.kernel.org/r/20250220134907.554085-9-maz@kernel.org
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>