dt-bindings: msm: disp: add yaml schemas for QCM2290 DPU bindings

QCM2290 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: Loic Poulain <loic.poulain@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Patchwork: https://patchwork.freedesktop.org/patch/474091/
Link: https://lore.kernel.org/r/1644852547-10067-2-git-send-email-loic.poulain@linaro.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>