fix(wireless): Fix undefined behavior when wireless radio is 6g band …

[VGDSpehar]

…capable

Falling back on 5g band when the radio is configured by default for 6g band. 6g band is restricted to indoor uses in most places, and require wpa3.

Related issue : #1180

[ilario]

Thanks @VGDSpehar !!

I don't have 6GHz-capable routers, but I quickly checked with the routers I have (2.4+5 or only 2.4) and there is no negative impact due to this PR on those devices.

If in the future someone gets their hands on a 6GHz device, we can expand the support to 6GHz, but so far I completely agree with @VGDSpehar 's approach: let's ignore 6GHz.

Some background on 6GHz for future reference:

It is allowed, alas with very low power, in more than half of the countries:
https://git.kernel.org/pub/scm/linux/kernel/git/wens/wireless-regdb.git/tree/db.txt?id=HEAD

In OpenWrt's table of hardware, there a few routers with 6 GHz radios, but they are all indoors ones: https://toh.openwrt.org

Wikipedia says that in Europe, only "low power indoor" is allowed and that "To help ensure they are used only indoors, these types of access points are not permitted to be connectorized for external antennas, weather-resistant, or run on battery power." https://en.m.wikipedia.org/wiki/List_of_WLAN_channels