ath9k: Fix BT_OP_SCAN usage

BT_OP_SCAN is applicable only for pre-MCI WLAN/BT combo chips
and using it for MCI-based cards is incorrect. Fix this by
cleaning up its usage.

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