net: mtk: wed: add dma mask limitation and GFP_DMA32 for device with more than 4GB DRAM

Limit tx/rx buffer address to 32-bit address space for board with more
than 4GB DRAM.

Fixes: 804775dfc2885 ("net: ethernet: mtk_eth_soc: add support for Wireless Ethernet Dispatch (WED)")
Fixes: 6757d345dd7db ("net: ethernet: mtk_wed: introduce hw_rro support for MT7988")
Tested-by: Daniel Pawlik <[e-mail]>
Tested-by: Matteo Croce <[e-mail]>
Signed-off-by: Rex Lu <[e-mail]>
Co-developed-by: Lorenzo Bianconi <[e-mail]>
Signed-off-by: Lorenzo Bianconi <[e-mail]>
Reviewed-by: Simon Horman <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/ethernet/mediatek/mtk_wed.c

···
 		void *buf;
 		int s;
 
-		page = __dev_alloc_page(GFP_KERNEL);
+		page = __dev_alloc_page(GFP_KERNEL | GFP_DMA32);
 		if (!page)
 			return -ENOMEM;
 
···
 		struct page *page;
 		int s;
 
-		page = __dev_alloc_page(GFP_KERNEL);
+		page = __dev_alloc_page(GFP_KERNEL | GFP_DMA32);
 		if (!page)
 			return -ENOMEM;
 
···
 	dev->wdma_idx = hw->index;
 	dev->version = hw->version;
 	dev->hw->pcie_base = mtk_wed_get_pcie_base(dev);
+
+	ret = dma_set_mask_and_coherent(hw->dev, DMA_BIT_MASK(32));
+	if (ret)
+		goto out;
 
 	if (hw->eth->dma_dev == hw->eth->dev &&
 	    of_dma_is_coherent(hw->eth->dev->of_node))