rockchip: dts: rk3328: support and enable dwc2

Enable dwc2 controller and add fixed regulator for dwc2 controller to
control vbus.

Signed-off-by: Meng Dongyang <daniel.meng@rock-chips.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Acked-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>