Input: xpad - add VID/PID for Razer Sabertooth

The xpad driver recognizes Razer Sabertooth controllers as generic xbox
controller, while it is really a 360 controller.  This patch adds pid/vid
mappings for the controller so that it is correctly recognized.

Signed-off-by: Frank Razenberg <frank@zzattack.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>