myri10ge: Simplify DMA setting

As stated in [1], dma_set_mask() with a 64-bit mask will never fail if
dev->dma_mask is non-NULL.
So, if it fails, the 32 bits case will also fail for the same reason.

If dma_set_mask_and_coherent() succeeds, 'dac_enabled' 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/e92b0c3a3c[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/ethernet/myricom/myri10ge/myri10ge.c

···
 	struct myri10ge_priv *mgp;
 	struct device *dev = &pdev->dev;
 	int status = -ENXIO;
-	int dac_enabled;
 	unsigned hdr_offset, ss_offset;
 	static int board_number;
 
···
 
 	myri10ge_mask_surprise_down(pdev);
 	pci_set_master(pdev);
-	dac_enabled = 1;
 	status = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(64));
-	if (status != 0) {
-		dac_enabled = 0;
-		dev_err(&pdev->dev,
-			"64-bit pci address mask was refused, trying 32-bit\n");
-		status = dma_set_mask(&pdev->dev, DMA_BIT_MASK(32));
-	}
 	if (status != 0) {
 		dev_err(&pdev->dev, "Error %d setting DMA mask\n", status);
 		goto abort_with_enabled;
···
 	/* fake NETIF_F_HW_VLAN_CTAG_RX for good GRO performance */
 	netdev->hw_features |= NETIF_F_HW_VLAN_CTAG_RX;
 
-	netdev->features = netdev->hw_features;
-
-	if (dac_enabled)
-		netdev->features |= NETIF_F_HIGHDMA;
+	netdev->features = netdev->hw_features | NETIF_F_HIGHDMA;
 
 	netdev->vlan_features |= mgp->features;
 	if (mgp->fw_ver_tiny < 37)