KVM: arm64: Make all 32bit ID registers fully writable

KVM: arm64: Make all 32bit ID registers fully writable

32bit ID registers aren't getting much love these days, and are
often missed in updates. One of these updates broke restoring
a GICv2 guest on a GICv3 machine.

Instead of performing a piecemeal fix, just bite the bullet
and make all 32bit ID regs fully writable. KVM itself never
relies on them for anything, and if the VMM wants to mess up
the guest, so be it.

Fixes: 5cb57a1aff755 ("KVM: arm64: Zero ID_AA64PFR0_EL1.GIC when no GICv3 is presented to the guest")
Reported-by: Peter Maydell <peter.maydell@linaro.org>
Cc: stable@vger.kernel.org
Reviewed-by: Oliver Upton <oupton@kernel.org>
Link: https://patch.msgid.link/20251030122707.2033690-2-maz@kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>