arm64: dts: meson: g12a: Add G12A USB nodes

This patch adds the nodes for the USB Complex found in the Amlogic
G12A SoC.

It includes the :
- 2 USB2 PHYs
- 1 USB3 + PCIE Combo PHY
- the USB Glue with it's DWC2 and DWC3 sub-nodes

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>