block: change return type to bool

Because blk_do_io_stat() only does a judgement about the request
contributes to IO statistics, it better changes return type to bool.

Signed-off-by: Chengguang Xu <cgxu519@gmx.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk.h

@@ -297,7 +297,7 @@ extern int blk_update_nr_requests(struct request_queue *, unsigned int);
  *	b) the queue had IO stats enabled when this request was started, and
  *	c) it's a file system request
  */
-static inline int blk_do_io_stat(struct request *rq)
+static inline bool blk_do_io_stat(struct request *rq)
 {
 	return rq->rq_disk &&
 	       (rq->rq_flags & RQF_IO_STAT) &&