operating standard and supported standard proposal

For getting wifi supported standards nl80211 interface is used as it was already implemented in nlwifi. It is easy there to get radio capabilities which as I guess is the same what supported standards is. By supported standard I understand wifi standards that radio hardware supports (it is capable of acting in that standard). For particular radio hardware supported standards are constant.

As operating standard I understand current wifi standard. For example on radio capable of 80211ac standard it is possible to run AP in 80211a, on 80211n capable radion it is possible to run AP on 80211g or 80211b or even both.

Current wifimngr implementation provides only operating standard information, I can add additional parameter to show also supported standard (in separate merge request).

Some test results can be found in task: https://project.iopsys.eu/issues/3029 @janusz @anjancx Please take a look.