blk-mq-sched: remove unused 'can_block' arg from blk_mq_sched_insert_request

After commit:

923218f6166a ("blk-mq: don't allocate driver tag upfront for flush rq")

we no longer use the 'can_block' argument in
blk_mq_sched_insert_request(). Kill it.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>

Added actual commit message as to why it's being removed.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/block/blk-mq-sched.h b/block/blk-mq-sched.h
index ba1d141..1e9c901 100644
--- a/block/blk-mq-sched.h
+++ b/block/blk-mq-sched.h
@@ -18,7 +18,7 @@
 void blk_mq_sched_restart(struct blk_mq_hw_ctx *hctx);
 
 void blk_mq_sched_insert_request(struct request *rq, bool at_head,
-				 bool run_queue, bool async, bool can_block);
+				 bool run_queue, bool async);
 void blk_mq_sched_insert_requests(struct request_queue *q,
 				  struct blk_mq_ctx *ctx,
 				  struct list_head *list, bool run_queue_async);