This is used by the 'athsurvey' command to print out channel survey
statistics - % busy times transmit, receive and airtime.
It's as buggy and incomplete as the rest of the HAL survey support -
notably, tying into the ANI code to read channel stats and occasionally
getting garbage counters isn't very nice. It also doesn't (yet!) get
channel survey information during a scan. But it's good enough for
basic air-time debugging, which is why I'm committing it in this state.
Tested:
* AR9380, STA mode
AR9462/AR9565.
This and some upcoming changes to the HAL for these chips should
address some of the signal sensitivity reported by users.
Tested:
* AR9462 (WB222), STA mode
Obtained from: Linux ath9k
work in FreeBSD.
This is still heavily a work in progress but I'd rather it start
shipping in -HEAD sooner rather than later.
This doesn't (yet) link it into the build system either for a static
kernel or as a module; that will come later (after many, many make universe
tests.)
