netxen: Notify firmware of Flex-10 interface down

Notify firmware when a Flex-10 interface is brought down
so that virtual connect manager can display the correct link status.

Signed-off-by: Sony Chacko <sony.chacko@qlogic.com>
Signed-off-by: Amit Kumar Salecha <amit.salecha@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>