Bring over the initial 802.11n bluetooth coexistence support code.

The Linux ath9k btcoex code is based off of this code.

Note this doesn't actually implement functional btcoex; there's some
driver glue and a whole lot of verification that is required.

On the other hand, I do have the AR9285+BT and AR9287+BT NICs which
this code supports..

Obtained from: Qualcomm Atheros, Linux ath9k