For now, the diversity settings are controlled by 'txantenna',
-not- rxantenna. This is because the earlier chipsets had
controllable TX diversity; the RX antenna setting twiddles
the default antenna register. I'll try sort that stuff out at
some point.
Call the antenna switch function from the board setup function
so scans, channel changes, mode changes, etc don't set the
diversity back to a default state too far from what's intended.
Things to todo:
* Squirrel away the last antenna diversity/combining parameters
and restore them during board setup if HAL_ANT_VARIABLE is
defined. That way scans, etc don't reset the diversity settings.
* Add some more public facing statistics, rather than what's
simply logged under HAL_DEBUG_DIVERSITY.
For now, the fixed antenna settings behave better than variable
settings for me. I have some further fiddling to do..
Obtained from: Atheros
08e0a0c638