bfq: don't duplicate code for different paths

As we can see, returns parent_sched_may_change whether
sd->next_in_service changes or not, so remove this judgment.
Signed-off-by: huhai <huhai@tj.kylinos.cn>
Acked-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/bfq-wf2q.c

@@ -137,9 +137,6 @@ static bool bfq_update_next_in_service(struct bfq_sched_data *sd,
 
 	sd->next_in_service = next_in_service;
 
-	if (!next_in_service)
-		return parent_sched_may_change;
-
 	return parent_sched_may_change;
 }