blk-mq: mark __blk_mq_complete_request() static

It's no longer used outside of blk-mq core.

Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 86bd5b2..3ae09de 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -358,7 +358,7 @@
 	put_cpu();
 }
 
-void __blk_mq_complete_request(struct request *rq)
+static void __blk_mq_complete_request(struct request *rq)
 {
 	struct request_queue *q = rq->q;