block: Fix documentation for blkdev_issue_flush()

Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

block/blk-barrier.c

@@ -302,7 +302,7 @@ static void bio_end_empty_barrier(struct bio *bio, int err)
  * Description:
  *    Issue a flush for the block device in question. Caller can supply
  *    room for storing the error offset in case of a flush error, if they
- *    wish to.  Caller must run wait_for_completion() on its own.
+ *    wish to.
  */
 int blkdev_issue_flush(struct block_device *bdev, sector_t *error_sector)
 {