mac80211: avoid using uninitialized stack data

Avoid a case where we would access uninitialized stack data if the AP
advertises HT support without 40MHz channel support.

Cc: stable@vger.kernel.org
Fixes: f3000e1b ("mac80211: fix broken use of VHT/20Mhz with some APs")
Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/mlme.c

@@ -174,6 +174,7 @@ ieee80211_determine_chantype(struct ieee80211_sub_if_data *sdata,
 	if (!(ht_cap->cap_info &
 	      cpu_to_le16(IEEE80211_HT_CAP_SUP_WIDTH_20_40))) {
 		ret = IEEE80211_STA_DISABLE_40MHZ;
+		vht_chandef = *chandef;
 		goto out;
 	}