virtio-blk: Use kobj_to_dev() instead of container_of()

Use kobj_to_dev() instead of container_of()
Signed-off-by: NTian Tao <tiantao6@hisilicon.com>
Reviewed-by: NBart Van Assche <bvanassche@acm.org>
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: NStefano Garzarella <sgarzare@redhat.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

drivers/block/virtio_blk.c

@@ -646,7 +646,7 @@ static struct attribute *virtblk_attrs[] = {
 static umode_t virtblk_attrs_are_visible(struct kobject *kobj,
 		struct attribute *a, int n)
 {
-	struct device *dev = container_of(kobj, struct device, kobj);
+	struct device *dev = kobj_to_dev(kobj);
 	struct gendisk *disk = dev_to_disk(dev);
 	struct virtio_blk *vblk = disk->private_data;
 	struct virtio_device *vdev = vblk->vdev;