ASoC: dt-bindings: mediatek,mt8188-mt6359: add mt8188-mt6359 document

Add document for mt8188 board with mt6359.

Signed-off-by: Trevor Wu <trevor.wu@mediatek.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230116034131.23943-14-trevor.wu@mediatek.com


Signed-off-by: Mark Brown <broonie@kernel.org>