nvme-pci: remove unnecessary nested locking

The nvme pci driver no longer handles completions under the cq lock,
so the nested locking is not necessary.

Signed-off-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/nvme/host/pci.c

@@ -2012,13 +2012,7 @@ static void nvme_del_cq_end(struct request *req, blk_status_t error)
 	if (!error) {
 		unsigned long flags;
 
-		/*
-		 * We might be called with the AQ cq_lock held
-		 * and the I/O queue cq_lock should always
-		 * nest inside the AQ one.
-		 */
-		spin_lock_irqsave_nested(&nvmeq->cq_lock, flags,
-					SINGLE_DEPTH_NESTING);
+		spin_lock_irqsave(&nvmeq->cq_lock, flags);
 		nvme_process_cq(nvmeq, &start, &end, -1);
 		spin_unlock_irqrestore(&nvmeq->cq_lock, flags);