dt-bindings: display/msm: gpu: add rbcpr clock

Describe the RBCPR clock used on msm8996 (A530), MSM8998 (A540) and
SDM630/660 (A508/A512).

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/517470/
Link: https://lore.kernel.org/r/20230109054407.330839-1-dmitry.baryshkov@linaro.org


Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>