ath9k: Fix chip wakeup issue

Waking up the chip after powering it down fails sometimes.
In this case the CPU is locked for 200ms. Reduce this
interval to 10ms to avoid excessive busy looping.

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