Add DFS signal detection entry to router logging categories

Now that AX capable routers are running out the door, to get full use of WiFi 6 capabilities, there will be more use of DFS channels.

It would be wonderful if Netgear would add router log entries for when DFS signal detection is seen and the router is reset from 160MHz channel to 80Mhz channels.

At the present time, we do not know if there was actually a DFS signal detection or whether the router itself just malfunctioned and dropped from 160MHz channel to 80MHz channel.

You can make it a selectable log entry so people can decide whether or not they want to see it in the logs.