It isn't linked into the build because it's missing the TX power
and PDADC programming code.
This code is mostly based on the ath9k codebase, compared against
the Atheros codebase as appropriate.
What's implemented:
* probe/attach
* EEPROM board value programming
* RX initial calibration
* radio channel programming
* general MAC / baseband setup
* async fifo setup
* open-loop tx power calibration
What's missing before it can be enabled by default:
* TX power / calibration setting code
* closed-loop tx power calibration routines
* TSF2 handling
* generic timer support from ath9k
Obtained from: Atheros, ath9k
