Input: add ST1232 touchscreen controller driver

This patch introduces support for Sitronix ST1232 integrated capacitive
touchscreen with LCD module. The touchscreen is multitouch capable and
can report coordinates of up to two contact points.

Signed-off-by: Tony SIM <chinyeow.sim.xt@renesas.com>
Reviewed-by: Trilok Soni <tsoni@codeaurora.org>
Acked-by: Henrik Rydberg <rydberg@euromail.se>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>