blk-mq: add blktrace insert event trace

We need it to make 'btt' from blktrace happy, otherwise
we are missing one state transition.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-mq.c

@@ -721,6 +721,8 @@ static void __blk_mq_insert_request(struct blk_mq_hw_ctx *hctx,
 {
 	struct blk_mq_ctx *ctx = rq->mq_ctx;
 
+	trace_block_rq_insert(hctx->queue, rq);
+
 	list_add_tail(&rq->queuelist, &ctx->rq_list);
 	blk_mq_hctx_mark_pending(hctx, ctx);