Add DT bindings documentation for the Everest-semi ES8311 codec.

Everest-semi ES8311 codec is a low-power mono audio codec with I2S audio
interface and I2C control.
Signed-off-by: Matteo Martelli <matteomartelli3@gmail.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://msgid.link/r/20240522164722.954656-2-matteomartelli3@gmail.comSigned-off-by: Mark Brown <broonie@kernel.org>