[SCSI] fcoe: remove fcoe_interface->priv pointer

The priv pointer is no longer needed, and once NPIV is enabled
fcoe_interface:fc_lport becomes a one-to-many relationship.

Remove the single pointer.

Signed-off-by: Chris Leech <christopher.leech@intel.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>