ath9k: Summarize hw state per channel context

Group and set hw state (opmode, primary_sta, beacon conf) per
channel context instead of whole list of vifs. This would allow
each channel context to run in different mode (STA/AP).

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