dt-bindings: input: Convert ChipOne ICN8318 binding to a schema

The ChipOne ICN8318 Touchscreen Controller is supported by Linux thanks
to its device tree binding.

Now that we have the DT validation in place, let's convert the device
tree bindings for that driver over to a YAML schema.

Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20210721140424.725744-17-maxime@cerno.tech


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