HID: wacom - Cleanup touch arbitration logic

stylus_in_proximity was introduced to support touch arbitration
before in range was supported. With in range event, the logic
changed. stylus_in_proximity should be set for both in prox and
in range events.

To finish a clean touch arbitration logic, we should send touch
up (if it was down) before posting any general pen events.

Signed-off-by: Ping Cheng <pingc@wacom.com>
Reviewed-by: Jason Gerecke <jason.gerecke@wacom.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>