dt-bindings: usb: realtek,rts5411: Add missing "additionalProperties" on child nodes

All nodes need an explicit additionalProperties or unevaluatedProperties
unless a $ref has one that's false. As that is not the case with
usb-device.yaml, "additionalProperties" is needed here.

Fixes: c44d9dab31d6 ("dt-bindings: usb: Add downstream facing ports to realtek binding")
Signed-off-by: "Rob Herring (Arm)" <[e-mail]>
Reviewed-by: Stephen Boyd <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

Documentation/devicetree/bindings/usb/realtek,rts5411.yaml

···
     description: The hard wired USB devices
     type: object
     $ref: /schemas/usb/usb-device.yaml
+    additionalProperties: true
 
 required:
   - peer-hub