usb: dwc3: drd: Add support for usb-conn-gpio based usb-role-switch

usb-conn-gpio devices are a subnode of the USB interface controller, which
needs to be populated.
This allows having a non-type-c connector providing dual-role.

Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Link: https://lore.kernel.org/r/20220105071407.2240302-1-alexander.stein@ew.tq-group.com


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