scsi: NCR5380: Use DRIVER_SENSE to indicate valid sense data

When sense data is valid, call set_driver_byte(cmd, DRIVER_SENSE).  Otherwise
some callers of scsi_execute() will ignore sense data.  Don't set DID_ERROR or
DID_RESET just because sense data is missing.

Tested-by: Michael Schmitz <schmitzmic@gmail.com>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>