ath9k_hw: Fix frequent BT rx recovery

While resuming from S3, BT host issues HCI reset command and it
causes BT firmware to busy with security key calculation. At this
movement, WLAN detects MCI hardware error of MCI_CONT_INFO_TIMEOUT
and then it starts the recovery sequence repeatedly. Too many
recovery sequences would exhaust the BT kernel message pool. This
patch imposes a duration between consecutive BT recovery procedure.
Thus it solves BT firmware panic issue reported in AR9565.

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