dt-bindings: msm: disp: add yaml schemas for DPU bindings

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

Signed-off-by: Krishna Manikandan <mkrishn@codeaurora.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Link: https://lore.kernel.org/r/1621856653-10649-1-git-send-email-mkrishn@codeaurora.org


Signed-off-by: Rob Clark <robdclark@chromium.org>