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: c44d9dab

 ("dt-bindings: usb: Add downstream facing ports to realtek binding")
Signed-off-by: "Rob Herring (Arm)" <robh@kernel.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Link: https://lore.kernel.org/r/20240523194500.2958192-1-robh@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>