block, bfq: use helper macro RQ_BFQQ to get bfqq of request

Use helper macro RQ_BFQQ to get bfqq of request.
Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20230116095153.3810101-5-shikemeng@huaweicloud.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

block/bfq-iosched.c

@@ -6859,14 +6859,14 @@ static struct bfq_queue *bfq_init_rq(struct request *rq)
 		return NULL;
 
 	/*
-	 * Assuming that elv.priv[1] is set only if everything is set
+	 * Assuming that RQ_BFQQ(rq) is set only if everything is set
 	 * for this rq. This holds true, because this function is
 	 * invoked only for insertion or merging, and, after such
 	 * events, a request cannot be manipulated any longer before
 	 * being removed from bfq.
 	 */
-	if (rq->elv.priv[1])
-		return rq->elv.priv[1];
+	if (RQ_BFQQ(rq))
+		return RQ_BFQQ(rq);
 
 	bic = icq_to_bic(rq->elv.icq);