clk: qcom: mmcc-msm8996: Properly describe GPU_GX gdsc

The GPU_GX GDSC depends on both GPU GDSC being enabled and that the
VDD_GX rail is powered, so update the description of the node to cover
these requirements.

Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lkml.kernel.org/r/20200417070044.1376212-3-bjorn.andersson@linaro.org


Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>