[NET]: Add ethtool support for NETIF_F_IPV6_CSUM devices.

Add ethtool utility function to set or clear IPV6_CSUM feature flag.
Modify tg3.c and bnx2.c to use this function when doing ethtool -K
to change tx checksum.

Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/tg3.c b/drivers/net/tg3.c
index 32e4037..5ee1476 100644
--- a/drivers/net/tg3.c
+++ b/drivers/net/tg3.c
@@ -8318,7 +8318,7 @@
 
 	if (GET_ASIC_REV(tp->pci_chip_rev_id) == ASIC_REV_5755 ||
 	    GET_ASIC_REV(tp->pci_chip_rev_id) == ASIC_REV_5787)
-		ethtool_op_set_tx_hw_csum(dev, data);
+		ethtool_op_set_tx_ipv6_csum(dev, data);
 	else
 		ethtool_op_set_tx_csum(dev, data);