dt-bindings: clock: qcom: document the SM8650 GPU Clock Controller

Add bindings documentation for the SM8650 Graphics Clock Controller.

Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://lore.kernel.org/r/20231106-topic-sm8650-upstream-clocks-v3-4-761a6fadb4c0@linaro.org
Signed-off-by: Bjorn Andersson <andersson@kernel.org>