ath9k: Add appropriate ANI values for AP mode

The short calibration interval is different for AP
mode, fix this. Also, the timer should be rearmed in
the calibration routine during scanning.

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