Input: wacom_w8001 - add single-touch support

Emulate single-touch compatible events for the 2-finger panels
so that they can be used with single-touch legacy clients.

Assign device ids as Wacom USB vendor ID and product ID.
Name the device to reflect its specific features.

Scale touch coordinates to pen maximum if pen supported.

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