nvme-pci: Tidy up nvme_unmap_data

Remove pointless local variable and use rq_dma_dir macro.
Signed-off-by: Israel Rukshin <israelr@mellanox.com>
Reviewed-by: Max Gurtovoy <maxg@mellanox.com>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>

drivers/nvme/host/pci.c

@@ -537,14 +537,13 @@ static inline bool nvme_pci_use_sgls(struct nvme_dev *dev, struct request *req)
 static void nvme_unmap_data(struct nvme_dev *dev, struct request *req)
 {
 	struct nvme_iod *iod = blk_mq_rq_to_pdu(req);
-	enum dma_data_direction dma_dir = rq_data_dir(req) ?
-			DMA_TO_DEVICE : DMA_FROM_DEVICE;
 	const int last_prp = dev->ctrl.page_size / sizeof(__le64) - 1;
 	dma_addr_t dma_addr = iod->first_dma, next_dma_addr;
 	int i;
 
 	if (iod->dma_len) {
-		dma_unmap_page(dev->dev, dma_addr, iod->dma_len, dma_dir);
+		dma_unmap_page(dev->dev, dma_addr, iod->dma_len,
+			       rq_dma_dir(req));
 		return;
 	}