HID: wacom: Add reporting of wheel for Intuos4 WL

This patch adds reporting of ABS_WHEEL event. Raported walues are 0..71
and are related to absolute location of the finger on the wheel.

Signed-off-by: Przemo Firszt <przemo@firszt.eu>
Reviewed-by: Jason Gerecke <killertofu@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>