[PATCH] ide-scsi.c: fix ATAPI multi-lun support

ATAPI multi-lun support has been broken for a long time.

It used to be that "(drive->id->last_id & 0x7) + 1" was used as
shost->max_lun and the "hdXlun=" kernel parameter could be used to
override this value.

However it was far from optimal:
- people played with "hdXlun=" and then complained about multiple instances
  of the same device (most ATAPI drives respond to each LUN)
- probably some devices return 7 not 0 in id->last_id (=> 7 x same device)

This patch from Willem Riede <wrlk@riede.org> fixes it w/o need
for "hdXlun=" option.  It was tested by Willem on ATAPI PD/CD drive.

drivers/scsi/ide-scsi.c

@@ -1100,7 +1100,16 @@ static int idescsi_attach(ide_drive_t *drive)
 		return 1;
 
 	host->max_id = 1;
-	host->max_lun = 1;
+
+#if IDESCSI_DEBUG_LOG
+	if (drive->id->last_lun)
+		printk(KERN_NOTICE "%s: id->last_lun=%u\n", drive->name, drive->id->last_lun);
+#endif
+	if ((drive->id->last_lun & 0x7) != 7)
+		host->max_lun = (drive->id->last_lun & 0x7) + 1;
+	else
+		host->max_lun = 1;
+
 	drive->driver_data = host;
 	idescsi = scsihost_to_idescsi(host);
 	idescsi->drive = drive;