net/qla3xxx: 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.

So, if dma_set_mask_and_coherent() succeeds, 'pci_using_dac' is known to be
1.

Simplify code and remove some dead code accordingly.

[1]: https://lkml.org/lkml/2021/6/7/398

Signed-off-by: Christophe JAILLET <[e-mail]>
Link: https://lore.kernel.org/r/3011689e8c[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/ethernet/qlogic/qla3xxx.c

···
 	struct net_device *ndev = NULL;
 	struct ql3_adapter *qdev = NULL;
 	static int cards_found;
-	int pci_using_dac, err;
+	int err;
 
 	err = pci_enable_device(pdev);
 	if (err) {
···
 
 	pci_set_master(pdev);
 
-	if (!dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(64)))
-		pci_using_dac = 1;
-	else if (!(err = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32))))
-		pci_using_dac = 0;
-
+	err = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(64));
 	if (err) {
 		pr_err("%s no usable DMA configuration\n", pci_name(pdev));
 		goto err_out_free_regions;
···
 
 	qdev->msg_enable = netif_msg_init(debug, default_msg);
 
-	if (pci_using_dac)
-		ndev->features |= NETIF_F_HIGHDMA;
+	ndev->features |= NETIF_F_HIGHDMA;
 	if (qdev->device_id == QL3032_DEVICE_ID)
 		ndev->features |= NETIF_F_IP_CSUM | NETIF_F_SG;