[SCSI] scsi_debug: set resid to indicate no data-in when medium error

set resid to the requested data-in length when a MEDIUM ERROR is
simulated. This implies no valid data is returned in the data-in
buffer
Signed-off-by: NDouglas Gilbert <dgilbert@interlog.com>
Signed-off-by: NJames Bottomley <James.Bottomley@suse.de>

drivers/scsi/scsi_debug.c

@@ -1805,6 +1805,7 @@ static int resp_read(struct scsi_cmnd *SCpnt, unsigned long long lba,
 			devip->sense_buff[5] = (ret >> 8) & 0xff;
 			devip->sense_buff[6] = ret & 0xff;
 		}
+	        scsi_set_resid(SCpnt, scsi_bufflen(SCpnt));
 		return check_condition_result;
 	}