dt-bindings: display: msm: Add qcom, sm8350-mdss binding

Mobile Display Subsystem (MDSS) encapsulates sub-blocks
like DPU display controller, DSI etc. Add YAML schema for MDSS device
tree bindings

Signed-off-by: Robert Foss <robert.foss@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Patchwork: https://patchwork.freedesktop.org/patch/516338/
Link: https://lore.kernel.org/r/20221230153554.105856-3-robert.foss@linaro.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>