dt-bindings: display: samsung,exynos-hdmi-ddc: convert to dtschema

Convert the Exynos HDMI DDC bindings to DT schema format.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220208171823.226211-7-krzysztof.kozlowski@canonical.com