NetXen: Fix incorrect link status even with switch turned OFF.
NetXen driver failed to accurately indicate when a link is up or down.
This was encountered during failover testing, when the first port
indicated that the link was up even when the 10G switch it was assigned
to in the Bladecenter was turned off completely.

Signed-off by: Wen Xiong <wenxiong@us.ibm.com>
Signed-off by: Mithlesh Thukral <mithlesh@netxen.com>
Signed-off-by: NJeff Garzik <jeff@garzik.org>