* change the BB gating logic to explicitly define which chips are covered;
the ath9k method isn't as clear.
* don't disable the BB gating for now, the ar5416 initvals have it, and the
ar9160 initval sets it to 0x0. Figure out why before re-enabling this.
* migrate the Merlin (ar9280) applicable WAR from the Kite (ar9285) code
(which won't get called for Merlin!) and stuff it in here.