This removes the direct WME info access in the ieee80211com struct and instead
provides a method of fetching the data. Right now it's a no-op but eventually
it'll turn into a per-VAP method for drivers that support it (eg iwn, iwm,
upcoming ath10k work) as things like p2p support require this kind of behaviour.
Tested:
* ath(4), STA and AP mode
TODO:
* yes, this is slightly stack size-y, but it is an important first step
to get drivers migrated over to a sensible WME API. A lot of per-phy things
need to be converted to per-VAP before P2P, 11ac firmware, etc stuff shows up.