LinuxKPI: 802.11: implement cfg80211_{get,put}_bss

Implement cfg80211_{get,put}_bss currently doing malloc/free bits,
so hopefully the drivers get the calls right.

cfg80211_get_bss() sets up a lookup structure which may also take a
result (first hit wins) and calls ieee80211_scan_iterate() comparing
the various values in the iterator funcion. Some of the checks are
partially pointless (as it seems the drivers are not interested in
these parts [ANY] but we keep them for documentation purposes should
futher values arise in the future).

We currently only iterate over the first VAP which will do for now.

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