Some multi-interface devices support expresskeys on a separate interface,
such as Bamboo; some multi-interface devices do not support touch at all,
such as Pen only Intuos5. Make sure we report the right device names.
Tested-by: NJason Gerecke <killertofu@gmail.com>
Signed-off-by: NPing Cheng <pingc@wacom.com>
Signed-off-by: NDmitry Torokhov <dmitry.torokhov@gmail.com>