[SCSI] libfc, fcoe: Add FC passthrough support

This is the Open-FCoE implementation of the FC
passthrough support via bsg interface.

Passthrough support is added to both N_Ports and
VN_Ports.

Signed-off-by: Steve Ma <steve.ma@intel.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>