touchpad: Use remove callback to unlink event listener and stop timers

touchpad: Use remove callback to unlink event listener and stop timers

We use 2 mechanisms to unregister the trackpoint event listener depending on
device removal order.

1) We have a device_removed callback, if the trackpoint gets removed before
the touchpad, this gets called, sees the device being removed is the trackpoint
and unregisters the listener

2) If the touchpad gets removed first, then in tp_destroy we unregister the
listener

2) May be delayed beyond the destruction of the trackpoint itself if the
libinput user has a reference to the libinput_device for the touchpad.
When this happens the trackpoint still has an eventlistener at destroy time
and an assert triggers.

To fix this we must do 2) at the same time as we do 1), so at remove time.

While working on this I noticed that the touchpad code was also cancelling
timers at destroy time rather then remove time, which means that they may
expire between remove and destroy time, and cause events to be emitted from
a removed device, so this commit moves the cancelling of the timers to the
remove callback as well.

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