mac80211: reset ht_capab for each device

... or else "option htmode" is added multiple times to
the second and following device sections.

Signed-off-by: Reiner Herrmann <reiner@reiner-h.de>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@40711 3c298f89-4303-0410-b956-a3cf2f4a3e73

package/kernel/mac80211/files/lib/wifi/mac80211.sh

@@ -69,6 +69,7 @@ detect_mac80211() {
 		mode_band="g"
 		channel="11"
 		htmode=""
+		ht_capab=""
 
 		iw phy "$dev" info | grep -q 'Capabilities:' && htmode=HT20
 		iw phy "$dev" info | grep -q '2412 MHz' || { mode_band="a"; channel="36"; }