xen-blkfront: fix missing out label

Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

drivers/block/xen-blkfront.c

@@ -1232,6 +1232,7 @@ static int blkif_release(struct gendisk *disk, fmode_t mode)
 		kfree(info);
 	}
 
+out:
 	unlock_kernel();
 	return 0;
 }