arm64: dts: qcom: sc7180-idp: add vdds supply to the DSI PHY

Add the (required) vdss-supply property to the DSI PHY node.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20220706145412.1566011-3-dmitry.baryshkov@linaro.org