scsi: target: Add device product id and revision configfs attributes
The product_id and revision attributes will allow for the modification of
the T10 Model and Revision strings returned in inquiry responses. Its
value can be viewed and modified via the ConfigFS path at:
Signed-off-by: Alan Adamson <alan.adamson@oracle.com> Reviewed-by: Bart Van Assche <bvanassche@acm.org> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>