virtio/s390: use dev_to_virtio

Use dev_to_virtio() instead of open-coding it.
Signed-off-by: Geliang Tang <geliangtang@163.com>
Message-Id: <912bf59bd3a48f2d4d4994681e898dc084fe29d3.1451484163.git.geliangtang@163.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/s390/virtio/virtio_ccw.c

@@ -945,8 +945,7 @@ static struct virtio_config_ops virtio_ccw_config_ops = {
 
 static void virtio_ccw_release_dev(struct device *_d)
 {
-	struct virtio_device *dev = container_of(_d, struct virtio_device,
-						 dev);
+	struct virtio_device *dev = dev_to_virtio(_d);
 	struct virtio_ccw_device *vcdev = to_vc_device(dev);
 
 	kfree(vcdev->status);