dt-bindings: usb: genesys,gl850g: allow downstream device subnodes

dt-bindings: usb: genesys,gl850g: allow downstream device subnodes

As this binding describes USB hubs, it's natural for them to have
downstream devices.

Change "additionalProperties" to "unevaluatedProperties" to allow
properties defined in usb-device.yaml (for DT cells properties) and add
a pattern-based downstream device subnode rule to match those subnodes.

These changes allow downstream devices get defined under the hub.

Signed-off-by: Icenowy Zheng <uwu@icenowy.me>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20240917094008.283529-1-uwu@icenowy.me
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>