prj.conf: Enable UART0 for console

To use it you need USB/UART adapter wired this way:

                  G x R T
      +-o-(...)-o-o-o-o-o-+
 USB =| ArduinoNano BLE S |
      +-o-(...)-o-o-o-o-o-+

Then connect using:

screen -U /dev/ttyUSB0 115200
uart:~$ device list
- UART_0 (READY)
uart:~$ kernel version
Zephyr version 3.1.0
ot version
OPENTHREAD/e2a765599; Zephyr; Sep  6 2022 19:58:28
Done

Relate-to: meta-oniro-blueprints-gateway#6 Origin: https://gitlab.eclipse.org/pcoval/openthread-node-zephyr Signed-off-by: Philippe Coval philippe.coval.ext@huawei.com