fcoe: Update multicast addresses on FIP mode change

When the FIP mode is changed we need to update the multicast addresses
to ensure we get the correct frames.

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>