wlan - Update ath, sync rev 1.276@FreeBSD

wlan - Update ath, sync rev 1.276@FreeBSD

* Don't delay updating the longcal timer - instead, update the longcal
  flag immediately so it's only set once per longcal interval.

  Without this, the current AR5416 code will continuously spam NF
  calibrations during a periodic calibration if the longcal flag
  is set. The longcal flag wouldn't be cleared until the calibration
  method indicates that calibrations are "complete".

  This could cause numerous problems including stuck beacons.

Taken-From: FreeBSD