dt-bindings: display: Add ingenic,jz4780-dw-hdmi DT Schema

Add DT bindings for the hdmi driver for the Ingenic JZ4780 SoC.
Based on .txt binding from Zubair Lutfullah Kakakhel

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
Cc: Rob Herring <robh@kernel.org>
Cc: devicetree@vger.kernel.org
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Link: https://patchwork.freedesktop.org/patch/msgid/c806c6007f7bb090bf96ff6bd827f03e88bf4712.1644675566.git.hns@goldelico.com