blk-mq: fix bad clear of RQF_MQ_INFLIGHT in blk_mq_ct_ctx_init()

A previous commit moved the clearing of rq->rq_flags later,
but we may have already set RQF_MQ_INFLIGHT when that happens.
Ensure that we correctly initialize rq->rq_flags to the
right value.

This is based on an original fix by Ming, just rewritten to not
require a conditional.

Fixes: 7c3fb70f0341 ("block: rearrange a few request fields for better cache layout")
Reviewed-by:  Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-mq.c

@@ -269,13 +269,14 @@ static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
 {
 	struct blk_mq_tags *tags = blk_mq_tags_from_data(data);
 	struct request *rq = tags->static_rqs[tag];
+	req_flags_t rq_flags = 0;
 
 	if (data->flags & BLK_MQ_REQ_INTERNAL) {
 		rq->tag = -1;
 		rq->internal_tag = tag;
 	} else {
 		if (blk_mq_tag_busy(data->hctx)) {
-			rq->rq_flags = RQF_MQ_INFLIGHT;
+			rq_flags = RQF_MQ_INFLIGHT;
 			atomic_inc(&data->hctx->nr_active);
 		}
 		rq->tag = tag;
@@ -286,7 +287,7 @@ static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
 	/* csd/requeue_work/fifo_time is initialized before use */
 	rq->q = data->q;
 	rq->mq_ctx = data->ctx;
-	rq->rq_flags = 0;
+	rq->rq_flags = rq_flags;
 	rq->cpu = -1;
 	rq->cmd_flags = op;
 	if (data->flags & BLK_MQ_REQ_PREEMPT)