dt-bindings: display/msm: dsi-controller-main: Document qcom, master-dsi and qcom, sync-dual-dsi

This fixes warning:
  sm8250-xiaomi-elish-csot.dtb: dsi@ae94000: Unevaluated properties are not allowed ('qcom,master-dsi', 'qcom,sync-dual-dsi' were unexpected)
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Jianhua Lu <lujianhua000@gmail.com>
Fixes: 4dbe55c9 ("dt-bindings: msm: dsi: add yaml schemas for DSI bindings")
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/534306/
Link: https://lore.kernel.org/r/20230427122132.24840-1-lujianhua000@gmail.comSigned-off-by: Abhinav Kumar <quic_abhinavk@quicinc.com>

Documentation/devicetree/bindings/display/msm/dsi-controller-main.yaml

@@ -82,6 +82,18 @@ properties:
       Indicates if the DSI controller is driving a panel which needs
       2 DSI links.
 
+  qcom,master-dsi:
+    type: boolean
+    description: |
+      Indicates if the DSI controller is the master DSI controller when
+      qcom,dual-dsi-mode enabled.
+
+  qcom,sync-dual-dsi:
+    type: boolean
+    description: |
+      Indicates if the DSI controller needs to sync the other DSI controller
+      with MIPI DCS commands when qcom,dual-dsi-mode enabled.
+
   assigned-clocks:
     minItems: 2
     maxItems: 4