bfq: bfq_check_waker() should be static

It's only used in the same file, mark is appropriately static.

Fixes: 71217df3 ("block, bfq: make waker-queue detection more robust")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/bfq-iosched.c

@@ -1952,7 +1952,8 @@ static void bfq_update_io_intensity(struct bfq_queue *bfqq, u64 now_ns)
  *
  * On queue merging all waker information is lost.
  */
-void bfq_check_waker(struct bfq_data *bfqd, struct bfq_queue *bfqq, u64 now_ns)
+static void bfq_check_waker(struct bfq_data *bfqd, struct bfq_queue *bfqq,
+			    u64 now_ns)
 {
 	if (!bfqd->last_completed_rq_bfqq ||
 	    bfqd->last_completed_rq_bfqq == bfqq ||