ASoC: dt-bindings: rockchip: i2s-tdm: Document power-domains

The binding document is missing the power-domains property. Add it.

Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
Link: https://lore.kernel.org/r/20230315114806.3819515-7-cristian.ciocaltea@collabora.com


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