3rd generation Bamboo Pen and Touch tablets reuse the older
stylus packet but add an extra fixed zero pad byte to end.

The touch packets are quite different since it supports tracking
of up to 16 touches. The packet is 64-byte fixed size but contains
up to 15 smaller messages indicating data for a single touch or
for tablet button presses.
Signed-off-by: NChris Bagwell <chris@cnpbagwell.com>
Acked-by: NPing Cheng <pingc@wacom.com>
Signed-off-by: NDmitry Torokhov <dtor@mail.ru>