scsi: fcoe: correct sending FIP VLAN packets on VLAN 0

The FIP VLAN frame consists of an ethernet header followed
by the FIP VLAN frame, so we need to skip the ethernet header
if we want to check the FIP opcode.

Signed-off-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>