[SCSI] fc: Add GSPN_ID request to header file

Add request code and corresponding structs for "Get Symbolic Port
Name" (GSPN_ID) request.

Signed-off-by: Christof Schmitt <christof.schmitt@de.ibm.com>
Signed-off-by: Steffen Maier <maier@linux.vnet.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>