touchpad: if a palm touch moves out of the edge zone within a timeout, unpalm

touchpad: if a palm touch moves out of the edge zone within a timeout, unpalm

On small touchpads a touch that is intended to traverse much of the screen
width may start at the very edge, i.e. in the palm zone.
In that case, and if the touch moves out of the palm zone quickly enough, drop
the palm label and make it a normal touchpoint.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>