BoardConfig.mk: Clean up Wi-Fi stuff

Requires the http://github.com/alanorth/AR6kSDK.3.1 to be cloned
to hardware/atheros/AR6kSDK.3.1.
init.u8185.rc: Switch wpa_supplicant to use the super ghetto ar6000 driver

It's supported by the AR6SDK kernel driver and I couldn't get WEXT
or NL80211 working yet... note, this is also why I'm still using
wpa_supplicant 0.6 instead of 0.8+.