scsi: core: Use HCTX_TYPE_DEFAULT for blk_mq_tag_set->map

Use HCTX_TYPE_DEFAULT instead of 0 to avoid hardcoding.
Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/scsi_lib.c

@@ -1759,7 +1759,7 @@ static int scsi_map_queues(struct blk_mq_tag_set *set)
 
 	if (shost->hostt->map_queues)
 		return shost->hostt->map_queues(shost);
-	return blk_mq_map_queues(&set->map[0]);
+	return blk_mq_map_queues(&set->map[HCTX_TYPE_DEFAULT]);
 }
 
 void __scsi_init_queue(struct Scsi_Host *shost, struct request_queue *q)