net: broadcom: bcm4908_enet: fix received skb length

Use ETH_FCS_LEN instead of magic value and drop incorrect + 2
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/broadcom/bcm4908_enet.c

@@ -567,7 +567,7 @@ static int bcm4908_enet_poll(struct napi_struct *napi, int weight)
 
 		dma_unmap_single(dev, slot.dma_addr, slot.len, DMA_FROM_DEVICE);
 
-		skb_put(slot.skb, len - 4 + 2);
+		skb_put(slot.skb, len - ETH_FCS_LEN);
 		slot.skb->protocol = eth_type_trans(slot.skb, enet->netdev);
 		netif_receive_skb(slot.skb);