[ath] do a cold reset if TSFOOR triggers

TSFOOR happens if a beacon with a given TSF isn't received within the
programmed/expected TSF value, plus/minus a fudge range. (OOR == out of range.)

If this happens then it could be because the baseband/mac is stuck, or
the baseband is deaf.  So, do a cold reset and resync the beacon to
try and unstick the hardware.

It also happens when a bad AP decides to err, slew its TSF because they
themselves are resetting and they don't preserve the TSF "well."

This has fixed a bunch of weird corner cases on my 2GHz AP radio upstairs
here where it occasionally goes deaf due to how much 2GHz noise is up
here (and ANI gets a little sideways) and this unsticks the station
VAP.

For AP modes a hung baseband/mac usually ends up as a stuck beacon
and those have been addressed for a long time by just resetting the
hardware.  But similar hangs in station mode didn't have a similar
recovery mechanism.

Tested:

* AR9380, STA mode, 2GHz/5GHz
* AR9580, STA mode, 5GHz
* QCA9344 SoC w/ on-board wifi (TL-WDR4300/3600 devices); 2GHz
  STA mode

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