dt-bindings: msm/dsi: Don't require vdds-supply on 7nm PHY

On some SoCs (hello SM6375) vdds-supply is not wired to any smd-rpm
or rpmh regulator, but instead powered by the VDD_MX/mx.lvl line,
which is voted for in the DSI ctrl node.

Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/518513/
Link: https://lore.kernel.org/r/20230116115132.348961-1-konrad.dybcio@linaro.org


Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>