dt-bindings: sound: Convert Allwinner I2S binding to YAML

The Allwinner SoCs feature an I2S controller across multiple SoC
generations.

However, earlier generations were a bit simpler than the subsequent ones,
and for example would always have RX and TX capabilities, and no reset
lines.

Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>