arm64: dts: qcom: sc7180: drop #clock-cells from displayport-controller

Drop #clock-cells from DP device node. It is a leftover from the times
before splitting the device into controller and PHY devices. Now the
clocks are provided by the PHY, while the controller doesn't provide any
clocks.

Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20220710084133.30976-3-dmitry.baryshkov@linaro.org