Input: st1232 - switch to using MT-B protocol

Switch the driver to the slotted variant of multitouch protocol (MT-B)
with in-kernel tracking of the contacts.

Tested-by: Matthias Fend <Matthias.Fend@wolfvision.net>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>