netxen: enable LRO based on NETIF_F_LRO

o Enable/disable LRO in device based on NETIF_F_LRO flag, instead of using
  driver private flag.
o Disable LRO, if rx csum offloading is off.

David Miller,
	You should use netdev_info() instead of dev_info().

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>