Input: wacom - get rid of wacom_combo structure

Now that we moved input device from struct wacom to struct wacom_wac,
presence of wacom_combo just complicats things for no good reason.
Let's get rid of it and simply pass URB length to wacom_wac_irq().

Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

diff --cc drivers/input/tablet/wacom.h
Simple merge

diff --cc drivers/input/tablet/wacom_sys.c
Simple merge

diff --cc drivers/input/tablet/wacom_wac.c
Simple merge