dt-bindings: display/msm: add gcc-bus clock to dpu-smd845

Add gcc-bus clock required for the SDM845 DPU device tree node. This
change was made in the commit 111c5285 ("arm64: dts: qcom: sdm845:
move bus clock to mdp node for sdm845 target"), but was not reflected in
the schema.

Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/508379/
Link: https://lore.kernel.org/r/20221024164225.3236654-3-dmitry.baryshkov@linaro.org


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