boards: native_posix: add USB device controller binding and node

Current USB device controller drivers (drivers/usb/device)
do not use DEVICE_DT_GET but the properties from devicetree,
and USB device controller node is parent for CDC ACM UART and
AUDIO children nodes.

Add USB device controller binding and node to keep the samples
building for native_posix driver.

Signed-off-by: Johann Fischer <johann.fischer@nordicsemi.no>
2 files changed