dt-bindings: display/msm: split qcom, mdss bindings

dt-bindings: display/msm: split qcom, mdss bindings

Split Mobile Display SubSystem (MDSS) root node bindings to the separate
yaml file. Changes to the existing (txt) schema:
 - Added optional "vbif_nrt_phys" region used by msm8996
 - Made "bus" and "vsync" clocks optional (they are not used by some
   platforms)
 - Added optional resets property referencing MDSS reset
 - Defined child nodes pointing to corresponding reference schema.
 - Dropped the "lut" clock. It was added to the schema by mistake (it is
   a part of mdp4 schema, not the mdss).

Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/508378/
Link: https://lore.kernel.org/r/20221024164225.3236654-2-dmitry.baryshkov@linaro.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>