mac80211: fix VHT80 channel allocation (thx, SeG)

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@40770 3c298f89-4303-0410-b956-a3cf2f4a3e73

package/kernel/mac80211/files/lib/netifd/wireless/mac80211.sh

@@ -166,7 +166,7 @@ mac80211_hostapd_setup_base() {
 			append base_cfg "vht_oper_centr_freq_seg0_idx=$idx" "$N"
 		;;
 		VHT80)
-			case "$(( ($channel / 4) % 2 ))" in
+			case "$(( ($channel / 4) % 4 ))" in
 				1) idx=$(($channel + 6));;
 				2) idx=$(($channel + 2));;
 				3) idx=$(($channel - 2));;