ASoC: dt-bindings: convert amlogic,g12a-tohdmitx to dt-schema

Convert text bindings to dt-schema format for the Amlogic TX HDMI
control glue.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://msgid.link/r/20240606-topic-amlogic-upstream-bindings-convert-g12a-tohdmitx-v2-1-70d44fa30790@linaro.org
Signed-off-by: Mark Brown <broonie@kernel.org>