mac80211: avoid using ext NSS high BW if not supported

If the AP advertises inconsistent data, namely it has CCFS1 or CCFS2,
but doesn't advertise support for 160/80+80 bandwidth or "Extended NSS
BW Support", then we cannot use any MCSes in the the higher bandwidth.
Thus, avoid connecting with higher bandwidth since it's less efficient
that way.

Link: https://lore.kernel.org/r/20200528213443.0e55d40c3ccc.I6fd0b4708ebd087e5e46466c3e91f6efbcbef668@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/scan.c

@@ -132,6 +132,12 @@ ieee80211_update_bss_from_elems(struct ieee80211_local *local,
 			bss->beacon_rate =
 				&sband->bitrates[rx_status->rate_idx];
 	}
+
+	if (elems->vht_cap_elem)
+		bss->vht_cap_info =
+			le32_to_cpu(elems->vht_cap_elem->vht_cap_info);
+	else
+		bss->vht_cap_info = 0;
 }
 
 struct ieee80211_bss *