ASoC: dt-bindings: ssm2518: Convert to dtschema

Convert the ADI SSM2518 audio CODEC bindings to DT schema.

Signed-off-by: Marek Vasut <marex@denx.de>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230514225243.777504-1-marex@denx.de


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