scsi: fcoe: Harden CVL handling when we have not logged into the fabric.

If we haven't logged into the fabric yet we want to be a little more nuanced
with our CVL handling than what we've been:

- If the FCF has been selected, check the source MAC to make sure the frame is
from the FCF we've selected.
- If a FCF is selected and the CVL is from the FCF but we have not logged in
yet, then reset everything and go back to solicitation.

Signed-off-by: Chad Dupuis <chad.dupuis@cavium.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Acked-by: Johannes Thumshirn <jth@kernel.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>