amd-xgbe: Remove manual check and set of dma_mask pointer

The underlying device support will set the device dma_mask pointer
if DMA is set up properly for the device.  Remove the check for and
assignment of dma_mask when it is null. Instead, just error out if
the dma_set_mask_and_coherent function fails because dma_mask is null.
Signed-off-by: NTom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/amd/xgbe/xgbe-main.c

@@ -678,8 +678,6 @@ static int xgbe_probe(struct platform_device *pdev)
 	xgbe_default_config(pdata);
 
 	/* Set the DMA mask */
-	if (!dev->dma_mask)
-		dev->dma_mask = &dev->coherent_dma_mask;
 	ret = dma_set_mask_and_coherent(dev,
 					DMA_BIT_MASK(pdata->hw_feat.dma_width));
 	if (ret) {