Input: elantech - use firmware provided x, y ranges

With newer hardware, the touchpad provides range info.
Let's use it.

Signed-off-by: JJ Ding <jj_ding@emc.com.tw>
Acked-by: Daniel Kurtz <djkurtz@chromium.org>
Acked-by: Éric Piel <eric.piel@tremplin-utc.net>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>