loop: remove (now) unused 'out' label

gcc, righfully, complains:

drivers/block/loop.c:1369:1: warning: label 'out' defined but not used [-Wunused-label]

Kill it.
Signed-off-by: NJens Axboe <axboe@fb.com>

drivers/block/loop.c

@@ -1388,7 +1388,6 @@ static void lo_release(struct gendisk *disk, fmode_t mode)
 		loop_flush(lo);
 	}
 
-out:
 	mutex_unlock(&lo->lo_ctl_mutex);
 }