add simulate_radar entry to radio ubus call

New entry is added to radio API
simulate_radar

ubus call wifi.radio.xxx simulate_radar

This API will call driver specific implementation
to simulate radar detection event.
This API will apear for radio supporting 5G band
and having at least one AP interface.

Signed-off-by: Marek Puzyniak <marek.puzyniak@iopsys.eu>