ARM64: dts: meson-gxbb: add USB Nodes

Add the nodes for the dwc2 USB controller and the related USB PHYs.
Currently we force usb0 to host mode because OTG is currently not
working in our PHY driver.

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>