ath9k_htc: Stop ANI before doing hw_reset

During remain on channel request, ANI worker thread is not stopped
before doing hw reset. This is causing kernel crash in
hw_per_calibration. This change ensures that ANI is stopped before
doing chip reset and it will be rescheduled later when the chip is
configured back to home channel and having valid bss.

Reported-by: David Herrmann <dh.herrmann@gmail.com>
Tested-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Rajkumar Manoharan <rmanohar@qti.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>