dt-bindings: phy: rockchip: naneng-combphy: Add power-domains property

dt-bindings: phy: rockchip: naneng-combphy: Add power-domains property

Though isn't described in existing devicetrees, most Rockchip combphys
belong to a specific power-domain of the SoC. Taking RK3588 as example,
combphy 0 and combphy 2 belong to the PD_BUS domain. Document the
power-domains property to allow describing the information correctly
in devicetree.

Signed-off-by: Yao Zi <ziyao@disroot.org>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20250728102947.38984-4-ziyao@disroot.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>