Input: wacom - add Intuos5 multitouch sensor support

Intuos5 tablets with PTH-* model numbers include a multitouch sensor
which use the same touch reports as the 3rd-generation Bamboo. No
useful information is in the HID descriptor for the touch interface
so hardcoded values are used during setup.

Signed-off-by: Jason Gerecke <killertofu@gmail.com>
Reviewed-by: Chris Bagwell <chris@cnpbagwell.com>
Reviewed-by: Ping Cheng <pingc@wacom.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>