RDMA/pvrdma: Remove useless DMA-32 fallback configuration

As stated in [1], dma_set_mask() with a 64-bit mask never fails if
dev->dma_mask is non-NULL.

So, if it fails, the 32 bits case will also fail for the same reason.

Simplify code and remove some dead code accordingly.

[1]: https://lore.kernel.org/r/YL3vSPK5DXTNvgdx@infradead.org

Link: https://lore.kernel.org/r/10c29cb45d14fb8ed89cf1308c4a9a7d445c52eb.1641717275.git.christophe.jaillet@wanadoo.fr
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/hw/vmw_pvrdma/pvrdma_main.c

@@ -811,12 +811,10 @@ static int pvrdma_pci_probe(struct pci_dev *pdev,
 	}
 
 	/* Enable 64-Bit DMA */
-	if (dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(64)) != 0) {
-		ret = dma_set_mask(&pdev->dev, DMA_BIT_MASK(32));
-		if (ret != 0) {
-			dev_err(&pdev->dev, "dma_set_mask failed\n");
-			goto err_free_resource;
-		}
+	ret = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(64));
+	if (ret) {
+		dev_err(&pdev->dev, "dma_set_mask failed\n");
+		goto err_free_resource;
 	}
 	dma_set_max_seg_size(&pdev->dev, UINT_MAX);
 	pci_set_master(pdev);