[SCSI] fcoe: config via separate create_vn2vn module parameter

Add module parameter create_vn2vn that behaves like the create
parameter except that the new instance is created in FIP vn2vn mode.

This can be replaced once we change create to allow modifying
per-instance attributes before starting the instance.

Signed-off-by: Joe Eykholt <jeykholt@cisco.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>