usb: storage: shuttle_usbat: fix discs being detected twice

Even if the USB-to-ATAPI converter supported multiple LUNs, this
driver would always detect the same physical device or media because
it doesn't use srb->device->lun in any way.
Tested with an Hewlett-Packard CD-Writer Plus 8200e.

Signed-off-by: Daniele Forsi <dforsi@gmail.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/storage/shuttle_usbat.c

@@ -1851,7 +1851,7 @@ static int usbat_probe(struct usb_interface *intf,
 	us->transport_name = "Shuttle USBAT";
 	us->transport = usbat_flash_transport;
 	us->transport_reset = usb_stor_CB_reset;
-	us->max_lun = 1;
+	us->max_lun = 0;
 
 	result = usb_stor_probe2(us);
 	return result;