[ETHTOOL] Provide default behaviors for a few ethtool sub-ioctls

For the operations
	get-tx-csum
	get-sg
	get-tso
	get-ufo
the default ethtool_op_xxx behavior is fine for all drivers, so we
permit op==NULL to imply the default behavior.

This provides a more uniform behavior across all drivers, eliminating
ethtool(8) "ioctl not supported" errors on older drivers that had
not been updated for the latest sub-ioctls.

The ethtool_op_xxx() functions are left exported, in case anyone
wishes to call them directly from a driver-private implementation --
a not-uncommon case.  Should an ethtool_op_xxx() helper remain unused
for a while, except by net/core/ethtool.c, we can un-export it at a
later date.

[ Resolved conflicts with set/get value ethtool patch... -DaveM ]

Signed-off-by: Jeff Garzik <jeff@garzik.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/chelsio/cxgb2.c

@@ -794,9 +794,7 @@ static const struct ethtool_ops t1_ethtool_ops = {
 	.set_pauseparam    = set_pauseparam,
 	.get_rx_csum       = get_rx_csum,
 	.set_rx_csum       = set_rx_csum,
-	.get_tx_csum       = ethtool_op_get_tx_csum,
 	.set_tx_csum       = ethtool_op_set_tx_csum,
-	.get_sg            = ethtool_op_get_sg,
 	.set_sg            = ethtool_op_set_sg,
 	.get_link          = ethtool_op_get_link,
 	.get_strings       = get_strings,
@@ -804,7 +802,6 @@ static const struct ethtool_ops t1_ethtool_ops = {
 	.get_ethtool_stats = get_stats,
 	.get_regs_len      = get_regs_len,
 	.get_regs          = get_regs,
-	.get_tso           = ethtool_op_get_tso,
 	.set_tso           = set_tso,
 };