scsi: fnic: Enable fnic devcmd2 interface

This patch adds changes to check if fnic devcmd2 interface is exported by
the firmware. If devcmd2 interfaces is exported, driver starts using it
else falls back to fnic devcmd1 interface.

Signed-off-by: Satish Kharat <satishkh@cisco.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>