Fix hangs (exposed by spectral scan activity) in STA mode when the chip hangs.
Fix hangs (exposed by spectral scan activity) in STA mode when the
chip hangs.

* Always do a reset in ath_bmiss_proc(), regardless of whether the
  hardware is "hung" or not.  Specifically, for spectral scan, there's
  likely a whole bunch of potential hangs that we don't (yet) recognise
  in the HAL.  So to avoid staying RX deaf persisting until the station
  disassociates, just do a no-loss reset.

* Set sc_beacons=1 in STA mode.  During a reset, the beacon programming
  isn't done.  (It's likely I need to set sc_syncbeacons during a hang
  reset, but I digress.)  Thus after a reset, there's no beacon timer
  programming to send a BMISS interrupt if beacons aren't heard ..
  thus if the AP disappears, you won't get notified and you'll have to
  reset your interface.

This hasn't yet fixed all of the hangs that I've seen when debugging
spectral scan, but it's certainly reduced the hang frequency and it
should improve general STA stability in very noisy environments.

Tested:

* AR9280, STA mode, spectral scan off/on

PR:		kern/175227

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase