Input: wacom_serial4 - prepare for wacom USB moving to HID

wacom_wac.h will be moving to drivers/hid. Since we only need 3 definitions
from it let's simply copy them over.

Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>