tulip: Properly check dma mapping result

Tulip throws an error when dma debugging is enabled, as it doesn't properly
check dma mapping results with dma_mapping_error() durring tx ring refills.

Easy fix, just add it in, and drop the frame if the mapping is bad
Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
CC: Grant Grundler <grundler@parisc-linux.org>
CC: "David S. Miller" <davem@davemloft.net>
Reviewed-by: Grant Grundler <grundler@parisc-linux.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/dec/tulip/interrupt.c

@@ -76,6 +76,12 @@ int tulip_refill_rx(struct net_device *dev)
 
 			mapping = pci_map_single(tp->pdev, skb->data, PKT_BUF_SZ,
 						 PCI_DMA_FROMDEVICE);
+			if (dma_mapping_error(&tp->pdev->dev, mapping)) {
+				dev_kfree_skb(skb);
+				tp->rx_buffers[entry].skb = NULL;
+				break;
+			}
+
 			tp->rx_buffers[entry].mapping = mapping;
 
 			tp->rx_ring[entry].buffer1 = cpu_to_le32(mapping);