Main part of patch is adding support for a new Wacom MT touch
packet and labels these devices using MTSCREEN type.

Other items of interest:

Delete some duplicate code in HID parsing for Y info since
its already done in X path.

In wacom_query_tablet_data(), only invoke the set report
that requests tablets to send Wacom Touch packets for
Finger interfaces.  Mostly, this is to make code intent clear.
Tested-by: NJason Gerecke <killertofu@gmail.com>
Signed-off-by: NChris Bagwell <chris@cnpbagwell.com>
Signed-off-by: NPing Cheng <pingc@wacom.com>
Signed-off-by: NDmitry Torokhov <dtor@mail.ru>