dt-bindings: input/touchscreen: add bindings for zinitix

This patch adds dts bindings for the zinitix bt541 touchscreen.

Signed-off-by: Michael Srba <Michael.Srba@seznam.cz>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20201001122949.16846-2-michael.srba@seznam.cz


Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>