scsi: scsi_devinfo: handle non-terminated strings

devinfo->vendor and devinfo->model aren't necessarily
zero-terminated.

Fixes: b8018b97 "scsi_devinfo: fixup string compare"
Signed-off-by: Martin Wilck <mwilck@suse.com>
Reviewed-by: Bart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>