ASoC: dt-bindings: maxim,max9867: convert txt bindings to yaml

Convert from max9867.txt to maxim,max9867.yaml and add missing
'#sound-dai-cells' property.

Signed-off-by: Richard Leitner <richard.leitner@skidata.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230302-max9867-v2-1-fd2036d5e825@skidata.com


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