ath9k: Program HW for WB195 diversity

The MC_GAIN_CTL/CCK_DETECT registers have to be programmed
with the correct configuration values if WLAN/BT RX diversity
is enabled. Add this and also take care of the BTCOEX mode
when fast diversity is enabled/disabled.

Signed-off-by: Sujith Manoharan <c_manoha@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>