ath9k: Fix clearing of BTCOEX flags

BTCOEX flags are set/cleared by atomic operations.
We got to do the same in ath9k_btcoex_timer_resume,
while clearing those BTCOEX flags.

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