ath9k: Add channel context worker thread

The channel context worker is used to switch to next requested
channel context.

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>

drivers/net/wireless/ath/ath9k/beacon.c

@@ -80,7 +80,7 @@ static void ath9k_beacon_setup(struct ath_softc *sc, struct ieee80211_vif *vif,
 	u8 chainmask = ah->txchainmask;
 	u8 rate = 0;
 
-	sband = &common->sbands[common->hw->conf.chandef.chan->band];
+	sband = &common->sbands[sc->cur_chandef.chan->band];
 	rate = sband->bitrates[rateidx].hw_value;
 	if (vif->bss_conf.use_short_preamble)
 		rate |= sband->bitrates[rateidx].hw_value_short;