usb: misc: onboard-hub: support multiple power supplies

As some of the onboard hubs require multiple power supplies, provide the
environment to support them.

Signed-off-by: Benjamin Bara <benjamin.bara@skidata.com>
Acked-by: Matthias Kaehlcke <mka@chromium.org>
Link: https://lore.kernel.org/r/20230620-hx3-v7-1-f79b4b22a1bf@skidata.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>