hw/arm_gic: Add presave/postload hooks Add presave/postload hooks to the ARM GIC common base class. These will be used by the KVM in-kernel GIC subclass to sync state between kernel and userspace when migrating. Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Andreas Färber <afaerber@suse.de> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>