Input: wacom_w8001 - support pen or touch only devices

Not all penabled devices support touch. The same holds true for touch
devices, so we should be setting up devices according to the results
returned when we query the hardware.

Signed-off-by: Ping Cheng <pingc@wacom.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>