net80211 rate control statistics - first cut

[Adrian Chadd]

hiya,

here's the first cut of extracting data from the amrr rate control
module. I'd like to eventually migrate the ath_rate_sample code into
net80211 (which was done in a 2013 GSoC, but not finished enough to be
able to merge in.)

https://reviews.freebsd.org/D5630

It just exposes 'net.wlan.X.rate_stats' which will iterate through all
the nodes and list the current rate control stats. I haven't setup
urtwn in AP mode yet so I won't see its usefulness for AP mode
devices, but it should work.

I'd appreciate some feedback. I'd like to commit this soon and then
work on fixing up the rate control API and fix some locking issues.

Thanks!


-a