Input: psmouse - remove hardcoded touchpad size from the focaltech driver

The size has in most cases already been fetched from the touchpad, the
hardcoded values should have been removed.

Signed-off-by: Mathias Gottschlag <mgottschlag@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>