* For legacy NICs, the combined RSSI should be used.
For earlier AR5416 NICs, use control chain 0 RSSI rather than combined
RSSI.
For AR5416 > version 2.1, use the combined RSSI again.
* Add in a missing AR5212 HAL method (get11nextbusy) which may be called
by radar code.
This serves no functional change for what's currently in FreeBSD.