This device sometimes doesn't send touch release signals when moving
from >=4 fingers to <4 fingers. Using MT_QUIRK_NOT_SEEN_MEANS_UP instead
of MT_QUIRK_ALWAYS_VALID makes sure that no touches become stuck.

MT_QUIRK_FORCE_MULTI_INPUT is not necessary for this device, but does no
harm.
Signed-off-by: Sean O'Brien <seobrien@chromium.org>
Signed-off-by: Jiri Kosina <jkosina@suse.com>