dt-bindings: arm: Convert Realtek board/soc bindings to json-schema

Convert Realtek SoC bindings to DT schema format using json-schema.

Andreas is the only author and we agreed in person on licensing to be
GPL2+/BSD.

Cc: "Andreas Färber" <afaerber@suse.de>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: devicetree@vger.kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>