Input: st1232 - handle common DT bindings

This is required to specify generic touchscreen properties via DT.

Signed-off-by: Matthias Fend <matthias.fend@wolfvision.net>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>