ath9k: Remove pm_qos request after hw unregister.

Update pm_qos before removing it in deinit_device to prevent this
warning:

pm_qos_update_request() called for unknown object.

Signed-off-by: Vivek Natarajan <vnatarajan@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>