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/md/dm.c b/drivers/md/dm.c
index 9a0bdad..d5370a9 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -339,7 +339,7 @@
 	return md ? 0 : -ENXIO;
 }
 
-static int dm_blk_close(struct gendisk *disk, fmode_t mode)
+static void dm_blk_close(struct gendisk *disk, fmode_t mode)
 {
 	struct mapped_device *md = disk->private_data;
 
@@ -349,8 +349,6 @@
 	dm_put(md);
 
 	spin_unlock(&_minor_lock);
-
-	return 0;
 }
 
 int dm_open_count(struct mapped_device *md)