We assumed all touch interfaces report touch data. But, Bamboo
and Intuos non-touch devices report express keys on touch
interface. We need to check touch_max before counting touches.
Reported-by: NTasos Sahanidis <tasos@tasossah.com>
Signed-off-by: NPing Cheng <pingc@wacom.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>