block_device_operations->release() should return void

The value passed is 0 in all but "it can never happen" cases (and those
only in a couple of drivers) *and* it would've been lost on the way
out anyway, even if something tried to pass something meaningful.
Just don't bother.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index b7b7a88..04ca496 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -411,7 +411,7 @@
 	return 0;
 }
 
-static int rbd_release(struct gendisk *disk, fmode_t mode)
+static void rbd_release(struct gendisk *disk, fmode_t mode)
 {
 	struct rbd_device *rbd_dev = disk->private_data;
 	unsigned long open_count_before;
@@ -424,8 +424,6 @@
 	mutex_lock_nested(&ctl_mutex, SINGLE_DEPTH_NESTING);
 	put_device(&rbd_dev->dev);
 	mutex_unlock(&ctl_mutex);
-
-	return 0;
 }
 
 static const struct block_device_operations rbd_bd_ops = {