btrfs: assignment in write_dev_flush() doesn't need two semi-colons

One is enough.
Signed-off-by: NJesper Juhl <jj@chaosbits.net>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

fs/btrfs/disk-io.c

@@ -2732,7 +2732,7 @@ static int write_dev_flush(struct btrfs_device *device, int wait)
 	 * one reference for us, and we leave it for the
 	 * caller
 	 */
-	device->flush_bio = NULL;;
+	device->flush_bio = NULL;
 	bio = bio_alloc(GFP_NOFS, 0);
 	if (!bio)
 		return -ENOMEM;