Convert the Wolfson WM8960 audio codecs bindings to DT schema.

Changes against original binding:
1. Document clocks and clock-names - already present in DTS and used
   by Linux driver.
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20230217150627.779764-1-krzysztof.kozlowski@linaro.orgSigned-off-by: Mark Brown <broonie@kernel.org>