scsi: core: Add VENDOR_SPECIFIC sense code definitions

Some older devices will return vendor specific sense codes, so we should
be adding a definition for it.

Signed-off-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Bart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>