dt-bindings: display: st,stm32-dsi: Handle data-lanes in DSI port node

Handle 'data-lanes' property of the DSI output endpoint, it is possible
to describe DSI link with 1 or 2 data lanes this way.
Signed-off-by: Marek Vasut <marex@denx.de>
Link: https://lore.kernel.org/r/20220926234501.583115-1-marex@denx.deSigned-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/display/st,stm32-dsi.yaml

@@ -58,9 +58,20 @@ properties:
           DSI input port node, connected to the ltdc rgb output port.
 
       port@1:
-        $ref: /schemas/graph.yaml#/properties/port
-        description:
-          DSI output port node, connected to a panel or a bridge input port"
+        $ref: /schemas/graph.yaml#/$defs/port-base
+        unevaluatedProperties: false
+        description: |
+          DSI output port node, connected to a panel or a bridge input port.
+        properties:
+          endpoint:
+            $ref: /schemas/media/video-interfaces.yaml#
+            unevaluatedProperties: false
+            properties:
+              data-lanes:
+                minItems: 1
+                items:
+                  - const: 1
+                  - const: 2
 
 required:
   - "#address-cells"