mac80211: consider virtual mon when calculating min_def

When calculating the current max bw required for
a channel context, we didn't consider the virtual
monitor interface, resulting in its channel context
being narrower than configured.

This broke monitor mode with iwlmvm, which uses the
minimal width.
Reported-by: Ido Yariv <idox.yariv@intel.com>
Signed-off-by: Eliad Peller <eliadx.peller@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/chan.c

@@ -100,6 +100,12 @@ ieee80211_get_chanctx_max_required_bw(struct ieee80211_local *local,
 		}
 		max_bw = max(max_bw, width);
 	}
+
+	/* use the configured bandwidth in case of monitor interface */
+	sdata = rcu_dereference(local->monitor_sdata);
+	if (sdata && rcu_access_pointer(sdata->vif.chanctx_conf) == conf)
+		max_bw = max(max_bw, conf->def.width);
+
 	rcu_read_unlock();
 
 	return max_bw;