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

Convert the Exynos HDMI bindings to DT schema format.

The conversion includes also updates to the bindings, matching the
current DTS and Linux driver:
1. Add required properties: VDD supplies, power-domains.
2. Add optional properties: HDMI-EN supply, ports.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220208171823.226211-9-krzysztof.kozlowski@canonical.com