mac80211: TDLS: don't require beaconing for AP BW

Stop downgrading TDLS chandef when reaching the AP BW. The AP provides
the necessary regulatory protection in this case.

This fixes https://bugzilla.kernel.org/show_bug.cgi?id=153961, which
reported an infinite loop here.
Reported-by: Kamil Toman <kamil.toman@gmail.com>
Signed-off-by: Arik Nemtsov <arikx.nemtsov@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/tdls.c

@@ -333,10 +333,11 @@ ieee80211_tdls_chandef_vht_upgrade(struct ieee80211_sub_if_data *sdata,
 	if (!uc.center_freq1)
 		return;
 
-	/* proceed to downgrade the chandef until usable or the same */
+	/* proceed to downgrade the chandef until usable or the same as AP BW */
 	while (uc.width > max_width ||
+	       (uc.width > sta->tdls_chandef.width &&
 		!cfg80211_reg_can_beacon_relax(sdata->local->hw.wiphy, &uc,
-					      sdata->wdev.iftype))
+					       sdata->wdev.iftype)))
 		ieee80211_chandef_downgrade(&uc);
 
 	if (!cfg80211_chandef_identical(&uc, &sta->tdls_chandef)) {