netxen: convert to 64 bit statistics

Change to 64 bit statistics interface, driver was already maintaining 64 bit
value.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Acked-by: Amit Kumar Salecha <amit.salecha@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>