scsi: target: remove unused extension parameters

Reviewed-by: Mike Christie <mchristi@redhat.com>
Signed-off-by: David Disseldorp <ddiss@suse.de>
Link: https://lore.kernel.org/r/20190912095547.22427-4-ddiss@suse.de
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>