net: sgi: ioc3-eth: use csum_fold

replace open coded checksum folding by csum_fold.
Signed-off-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/sgi/ioc3-eth.c

@@ -1391,16 +1391,12 @@ static netdev_tx_t ioc3_start_xmit(struct sk_buff *skb, struct net_device *dev)
 		/* Sum up dest addr, src addr and protocol  */
 		ehsum = eh[0] + eh[1] + eh[2] + eh[3] + eh[4] + eh[5] + eh[6];
 
-		/* Fold ehsum.  can't use csum_fold which negates also ...  */
-		ehsum = (ehsum & 0xffff) + (ehsum >> 16);
-		ehsum = (ehsum & 0xffff) + (ehsum >> 16);
-
 		/* Skip IP header; it's sum is always zero and was
 		 * already filled in by ip_output.c
 		 */
 		csum = csum_tcpudp_nofold(ih->saddr, ih->daddr,
 					  ih->tot_len - (ih->ihl << 2),
-					  proto, 0xffff ^ ehsum);
+					  proto, csum_fold(ehsum));
 
 		csum = (csum & 0xffff) + (csum >> 16);	/* Fold again */
 		csum = (csum & 0xffff) + (csum >> 16);