ath9k: reduce baseband hang detection false positive rate

Check if the baseband state remains stable, and add a small delay
between register reads.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

diff --cc drivers/net/wireless/ath/ath9k/hw.c
Simple merge