fcoe: Use default VLAN for FIP VLAN discovery

FC-BB-6 states: FIP protocols shall be performed on a per-VLAN basis. It
is recommended to use the FIP VLAN discovery protocol on the default
VLAN.

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>