[ath] [ath_rate] Fix ANI calibration during non-ACTIVE states; start poking at rate control

These are some fun issues I've found with my upstairs wifi link at such a ridiculous
low signal level (like, < 5dB.)

• Add per-station tx/rx rssi statistics, in potential preparation to use that in the RX rate control.

• Call the rate control on each received frame to let it potentially use it as a hint for what rates to potentially use. It's a no-op right now.

• Do ANI calibration during scan as well. The ath_newstate() call was disabling the ANI timer and only re-enabling it during transitions to _RUN. This has the unfortunate side-effect that if ANI deafened the NIC because of interference and it disassociated, it wouldn't be reset and the scan would never hear beacons.

The ANI configuration is stored at least globally on some HALs and per-channel
on others. Because of this a NIC reset wouldn't help; the ANI parameters would
simply be programmed back in.

Now, I have a feeling I also need to do this during AUTH/ASSOC too and maybe,
if I'm feeling clever, I need to reset the ANI parameters on a given channel
during a transition through INIT or if the VAP is destroyed/re-created.
However for now this gets me out of the immediate weeds with connectivity
upstairs (and thus I /can/ commit); I'll keep chipping away at tidying this
stuff up in subsequent commits.

Tested:

• AR9344 (Wasp), 2G STA mode