[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/net/core/ethtool.c b/net/core/ethtool.c
index 8d5e5a0..0b531e9 100644
--- a/net/core/ethtool.c
+++ b/net/core/ethtool.c
@@ -52,6 +52,17 @@
 
 	return 0;
 }
+
+int ethtool_op_set_tx_ipv6_csum(struct net_device *dev, u32 data)
+{
+	if (data)
+		dev->features |= NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM;
+	else
+		dev->features &= ~(NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM);
+
+	return 0;
+}
+
 u32 ethtool_op_get_sg(struct net_device *dev)
 {
 	return (dev->features & NETIF_F_SG) != 0;
@@ -980,5 +991,6 @@
 EXPORT_SYMBOL(ethtool_op_set_tso);
 EXPORT_SYMBOL(ethtool_op_set_tx_csum);
 EXPORT_SYMBOL(ethtool_op_set_tx_hw_csum);
+EXPORT_SYMBOL(ethtool_op_set_tx_ipv6_csum);
 EXPORT_SYMBOL(ethtool_op_set_ufo);
 EXPORT_SYMBOL(ethtool_op_get_ufo);