dt-bindings: clock: qcom: Allow VDD_GFX supply to GX

In some designs the SoC's VDD_GFX pads are supplied by an external
regulator, rather than a power-domain. Allow this to be described in the
GPU clock controller binding.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Bjorn Andersson <quic_bjorande@quicinc.com>
Link: https://lore.kernel.org/r/20240125-sa8295p-gpu-v4-1-7011c2a63037@quicinc.com


Signed-off-by: Bjorn Andersson <andersson@kernel.org>