scsi: fcoe: Fixup missing initialisation in fcoe_dcb_create()

Found by 0-day robot.

Fixes: a99ac6e715bc ("scsi: fcoe: set default TC priority")
Signed-off-by: Hannes Reinecke <hare@suse.com>
Acked-by: Johannes Thumshirn <jth@kernel.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>