This patch add support to the 3 touch keys on Wacom Cintiq Pro.  These touch
keys are in the middle of the other two keys on the top edge of the tablet.
Signed-off-by: NPing Cheng <ping.cheng@wacom.com>
Reviewed-by: NBenjamin Tissoires <benjamin.tissoires@redhat.com>
Tested-by: NAaron Armstrong Skomra <aaron.skomra@wacom.com>
Acked-by: NDmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>