scsi: fcoe: set default TC priority

If DCB is not enabled or compiled in we still should be setting
a sane default priority. So put FCoE frames in priority class
'interactive' and FIP frames in priority class 'besteffort'.

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>