usb: misc: onboard_dev: add support for non-hub devices

usb: misc: onboard_dev: add support for non-hub devices

Most of the functionality this driver provides can be used by non-hub
devices as well.

To account for the hub-specific code, add a flag to the device data
structure and check its value for hub-specific code.

The 'always_powered_in_supend' attribute is only available for hub
devices, keeping the driver's default behavior for non-hub devices (keep
on in suspend).

Acked-by: Matthias Kaehlcke <mka@chromium.org>
Signed-off-by: Javier Carrasco <javier.carrasco@wolfvision.net>
Link: https://lore.kernel.org/r/20240325-onboard_xvf3500-v8-6-29e3f9222922@wolfvision.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>