ath9k_hw: Restore ANI registers to default during partial reset for AR9271

For AR9271 chips, if partial reset is done while scanning, the cycpwrThr1
will be set to maximum. This causes the degrade in DL throughput.
So restore the ANI registers to default during the partial reset.

Signed-off-by: Rajkumar Manoharan <rmanoharan@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>