dt-bindings: usb: mtu3: Add ports property

Define the ports property in the mediatek,mtu3 device tree binding schema.
Include definitions for port@0 and port@1, specifying their roles as
High Speed (HS) and Super Speed (SS) data buses, respectively.

Suggested-by: AngeloGioacchino Del Regno <[e-mail]>
Signed-off-by: Macpaul Lin <[e-mail]>
Reviewed-by: AngeloGioacchino Del Regno <[e-mail]>
Acked-by: Conor Dooley <[e-mail]>
Reviewed-by: Chunfeng Yun <[e-mail]>
Reviewed-by: Alexandre Mergnat <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: AngeloGioacchino Del Regno <[e-mail]>

Documentation/devicetree/bindings/usb/mediatek,mtu3.yaml

···
       property is used. See graph.txt
     $ref: /schemas/graph.yaml#/properties/port
 
+  ports:
+    $ref: /schemas/graph.yaml#/properties/ports
+
+    properties:
+      port@0:
+        $ref: /schemas/graph.yaml#/properties/port
+        description: High Speed (HS) data bus.
+
+      port@1:
+        $ref: /schemas/graph.yaml#/properties/port
+        description: Super Speed (SS) data bus.
+
   enable-manual-drd:
     $ref: /schemas/types.yaml#/definitions/flag
     description: