net: ethernet: mtk_eth_soc: set DMA coherent mask to get PPE working

Set DMA coherent mask to 32-bit which makes PPE offloading engine start
working on BPi-R4 which got 4 GiB of RAM.

Fixes: 2d75891 ("net: ethernet: mtk_eth_soc: support 36-bit DMA addressing on MT7988")
Suggested-by: Elad Yifee <eladwf@users.github.com>
Signed-off-by: Daniel Golle <daniel@makrotopia.org>
Link: https://lore.kernel.org/r/97e90925368b405f0974b9b15f1b7377c4a329ad.1706113251.git.daniel@makrotopia.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/mediatek/mtk_eth_soc.c

@@ -4761,7 +4761,10 @@ static int mtk_probe(struct platform_device *pdev)
 	}
 
 	if (MTK_HAS_CAPS(eth->soc->caps, MTK_36BIT_DMA)) {
-		err = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(36));
+		err = dma_set_mask(&pdev->dev, DMA_BIT_MASK(36));
+		if (!err)
+			err = dma_set_coherent_mask(&pdev->dev, DMA_BIT_MASK(32));
+
 		if (err) {
 			dev_err(&pdev->dev, "Wrong DMA config\n");
 			return -EINVAL;