netxen: fix tx csum status

Kernel default tx csum function (ethtool_op_get_tx_csum) doesn't show
correct csum status. It takes various FLAGS (NETIF_F_ALL_CSUM) in account
to show tx csum status, which driver doesn't set while disabling tx csum.

Signed-off-by: Sucheta Chakraborty <sucheta.chakraborty@qlogic.com>
Signed-off-by: Amit Kumar Salecha <amit.salecha@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>