deepin: only use BFQ as the elevator for single queue hdd devices

Question:
It is correct time to get the flag?

If we can get the flag,so we can only use BFQ elevator for hdd.
or it is same as before.

block/elevator.c

@@ -576,7 +576,8 @@ static struct elevator_type *elevator_get_default(struct request_queue *q)
 	    !blk_mq_is_shared_tags(q->tag_set->flags))
 		return NULL;
 #if defined(CONFIG_IOSCHED_BFQ)
-	return elevator_find_get(q, "bfq");
+	if (!blk_queue_nonrot(q))
+		return elevator_find_get(q, "bfq");
 #else
 	return elevator_find_get(q, "mq-deadline");
 #endif