be2net: log digital signature errors while flashing FW image

(based on a jumper setting on the adapter.) In this mode, the FW image when
flashed is authenticated with a digital signature. This patch logs
appropriate error messages and return a status to ethtool when errors
relating to FW image authentication occur.

Signed-off-by: Suresh Reddy <suresh.reddy@avagotech.com>
Signed-off-by: Sathya Perla <sathya.perla@avagotech.com>
Signed-off-by: David S. Miller <davem@davemloft.net>