wifi: mac80211: add consistency check for compat chandef

Add NULL check for compat variable to avoid crash in
cfg80211_chandef_compatible() if it got called with
some mixed up channel context where not all the users
compatible with each other, which shouldn't happen.

Signed-off-by: Anjaneyulu <pagadala.yesu.anjaneyulu@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20230616094948.ae0f10dfd36b.Iea98c74aeb87bf6ef49f6d0c8687bba0dbea2abd@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/chan.c

@@ -802,6 +802,11 @@ void ieee80211_recalc_chanctx_chantype(struct ieee80211_local *local,
 		}
 	}
 
+	if (WARN_ON_ONCE(!compat)) {
+		rcu_read_unlock();
+		return;
+	}
+
 	/* TDLS peers can sometimes affect the chandef width */
 	list_for_each_entry_rcu(sta, &local->sta_list, list) {
 		if (!sta->uploaded ||