nvme: add tracepoint for nvme_complete_rq

Add a tracepoint in nvme_complete_rq() for completions of NVMe commands. An
expmale output of the trace-point is as follows:

<idle>-0     [001] d.h.     3.505266: nvme_complete_rq: cmdid=989, qid=1, res=0, retries=0, flags=0x0, status=0

Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>
diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index f1430ca..b3af8e9 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -220,6 +220,8 @@ void nvme_complete_rq(struct request *req)
 {
 	blk_status_t status = nvme_error_status(req);
 
+	trace_nvme_complete_rq(req);
+
 	if (unlikely(status != BLK_STS_OK && nvme_req_needs_retry(req))) {
 		if (nvme_req_needs_failover(req, status)) {
 			nvme_failover_req(req);