[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/bnx2.c b/drivers/net/bnx2.c
index 4e5e1cb..d23861c 100644
--- a/drivers/net/bnx2.c
+++ b/drivers/net/bnx2.c
@@ -6218,7 +6218,7 @@
 	struct bnx2 *bp = netdev_priv(dev);
 
 	if (CHIP_NUM(bp) == CHIP_NUM_5709)
-		return (ethtool_op_set_tx_hw_csum(dev, data));
+		return (ethtool_op_set_tx_ipv6_csum(dev, data));
 	else
 		return (ethtool_op_set_tx_csum(dev, data));
 }