ath9k_htc: Handle IDLE state transition properly

Make sure that a chip reset is done when IDLE is turned
off - this fixes authentication timeouts.

Cc: stable@vger.kernel.org
Reported-by: Ignacy Gawedzki <i@lri.fr>
Signed-off-by: Sujith Manoharan <c_manoha@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>