Revert "nvme: use the DMA_ATTR_NO_WARN attribute"

BugLink: https://bugs.launchpad.net/bugs/1644596

This reverts commit 7c50722a.

The backports that fix bug #1633128 for xenial, in particular the backport
of upstream commit a9a62c93 ("dma-mapping: introduce the
DMA_ATTR_NO_WARN attribute"), introduce a regression.
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

drivers/nvme/host/pci.c

@@ -557,8 +557,7 @@ static int nvme_map_data(struct nvme_dev *dev, struct request *req,
 		goto out;
 
 	ret = BLK_MQ_RQ_QUEUE_BUSY;
-	if (!dma_map_sg_attrs(dev->dev, iod->sg, iod->nents, dma_dir,
-				DMA_ATTR_NO_WARN))
+	if (!dma_map_sg(dev->dev, iod->sg, iod->nents, dma_dir))
 		goto out;
 
 	if (!nvme_setup_prps(dev, req, blk_rq_bytes(req)))