ap: Fix invalid HT40 channel pair fallback

In case of incorrect HT40 configuration as part of an attempt to create
a 80 MHz AP, iface->conf->vht_oper_centr_freq_seg0_idx and
iface->conf->vht_oper_centr_freq_seg1_idx are zero'ed, but
iface->conf->vht_oper_chwidth remains VHT_CHANWIDTH_80MHZ. This causes
the logic in dfs_get_start_chan_idx to fail.

Fix this by setting iface->conf->vht_oper_chwidth to
VHT_CHANWIDTH_USE_HT when zero'ing the center frequency parameters.

Signed-off-by: Naftali Goldstein <naftali.goldstein@intel.com>

src/ap/hw_features.c

@@ -334,6 +334,7 @@ static void ieee80211n_check_scan(struct hostapd_iface *iface)
 		iface->conf->secondary_channel = 0;
 		iface->conf->vht_oper_centr_freq_seg0_idx = 0;
 		iface->conf->vht_oper_centr_freq_seg1_idx = 0;
+		iface->conf->vht_oper_chwidth = VHT_CHANWIDTH_USE_HT;
 		res = 1;
 		wpa_printf(MSG_INFO, "Fallback to 20 MHz");
 	}