input: touchscreen: mainstone: sync with zylonite driver

The two drivers are almost identical and can work on a variety
of hardware in principle. The mainstone driver supports additional
hardware, and the zylonite driver has a few cleanup patches.

Sync the two by adding the zylonite changes into the mainstone
one, and checking for the zylonite board to order to keep the
default behavior (interrupt enabled) there.

Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: linux-input@vger.kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>