Blackfin EMAC driver: fix bug - NAT doesn't work with bfin_mac driver

https://blackfin.uclinux.org/gf/project/uclinux-dist/forum/?action=ForumBrowse&forum_id=39&thread_id=23114&_forum_action=ForumMessageBrowse
Today I was dealing with the same problem, on my custom bf537 board, and bfin_mac driver.
I found that the problem is in setting ip_summed flag of skbuff structure,

Signed-off-by: Vitja Makarov <vitja.makarov@gmail.com>
Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>
Signed-off-by: Bryan Wu <bryan.wu@analog.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

drivers/net/bfin_mac.c

@@ -676,7 +676,7 @@ static void bf537mac_rx(struct net_device *dev)
 	skb->protocol = eth_type_trans(skb, dev);
 #if defined(BFIN_MAC_CSUM_OFFLOAD)
 	skb->csum = current_rx_ptr->status.ip_payload_csum;
-	skb->ip_summed = CHECKSUM_PARTIAL;
+	skb->ip_summed = CHECKSUM_COMPLETE;
 #endif
 
 	netif_rx(skb);