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/xen-blkfront.c b/drivers/block/xen-blkfront.c
index a894f88..d89ef86 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -1617,7 +1617,7 @@
 	return err;
 }
 
-static int blkif_release(struct gendisk *disk, fmode_t mode)
+static void blkif_release(struct gendisk *disk, fmode_t mode)
 {
 	struct blkfront_info *info = disk->private_data;
 	struct block_device *bdev;
@@ -1658,7 +1658,6 @@
 out:
 	bdput(bdev);
 	mutex_unlock(&blkfront_mutex);
-	return 0;
 }
 
 static const struct block_device_operations xlvbd_block_fops =