Revert "block: all blk-mq requests are tagged"

This reverts commit fb3ccb5d.

SCSI-2/SPI actually needs the tagged/untagged flag in the request to
work properly.  Revert this patch and add a follow on to set it in
the right place.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Acked-by: Jens Axboe <axboe@kernel.dk>
Reported-by: Meelis Roos <mroos@linux.ee>
Tested-by: Meelis Roos <mroos@linux.ee>
Cc: stable@vger.kernel.org

include/linux/blkdev.h

@@ -1136,8 +1136,7 @@ static inline bool blk_needs_flush_plug(struct task_struct *tsk)
 /*
  * tag stuff
  */
-#define blk_rq_tagged(rq) \
-	((rq)->mq_ctx || ((rq)->cmd_flags & REQ_QUEUED))
+#define blk_rq_tagged(rq)		((rq)->cmd_flags & REQ_QUEUED)
 extern int blk_queue_start_tag(struct request_queue *, struct request *);
 extern struct request *blk_queue_find_tag(struct request_queue *, int);
 extern void blk_queue_end_tag(struct request_queue *, struct request *);