sunxi: usbc: Add support for usb-vbus0 controller by axp drivebus pin

The axp221 / axp223's N_VBUSEN pin can be configured as an output rather
then an input, and this is used on some boards to control usb-vbus0, add
support for this.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>