buffer: remove unusued 'ret' variable

Merge hickup on my part, due to a clash between the writeback
changes and the EOPNOTSUPP removal in _submit_bh().

Signed-off-by: Jens Axboe <axboe@fb.com>

fs/buffer.c

@@ -3020,7 +3020,6 @@ static int submit_bh_wbc(int rw, struct buffer_head *bh,
 			 unsigned long bio_flags, struct writeback_control *wbc)
 {
 	struct bio *bio;
-	int ret = 0;
 
 	BUG_ON(!buffer_locked(bh));
 	BUG_ON(!buffer_mapped(bh));