ath9k_hw: Wait BT calibration to complete

Whenever BT calibration requested, WLAN has to wait for the
calibration to be completed. But right now we defer the waiting
which might cause BT calibration to fail. Fix that.

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