Document power-domains property in rockchip dw controller.

RV1126 is using eMMC and SDIO power domains but SDMMC is not.
Signed-off-by: Jagan Teki <jagan@edgeble.ai>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20221108041400.157052-3-jagan@edgeble.aiSigned-off-by: Ulf Hansson <ulf.hansson@linaro.org>