hw: arm_gic_kvm: Add KVM VGIC save/restore logic

Save and restore the ARM KVM VGIC state from the kernel.  We rely on
QEMU to marshal the GICState data structure and therefore simply
synchronize the kernel state with the QEMU emulated state in both
directions.

We take some care on the restore path to check the VGIC has been
configured with enough IRQs and CPU interfaces that we can properly
restore the state, and for separate set/clear registers we first fully
clear the registers and then set the required bits.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Message-id: 1392687921-26921-1-git-send-email-christoffer.dall@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
