KVM: arm64: nv: Save guest's ZCR_EL2 when in hyp context

When running a guest hypervisor, ZCR_EL2 is an alias for the counterpart
EL1 state.

Reviewed-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20240620164653.1130714-6-oliver.upton@linux.dev


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