mac80211: remove unnecessary BUG_ON()

The BUG_ON(!err) can't be triggered in the code path, so remove
it.
Signed-off-by: Zhao, Gang <gamerh2o@gmail.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/sta_info.c

@@ -552,7 +552,7 @@ static int sta_info_insert_finish(struct sta_info *sta) __acquires(RCU)
 int sta_info_insert_rcu(struct sta_info *sta) __acquires(RCU)
 {
 	struct ieee80211_local *local = sta->local;
-	int err = 0;
+	int err;
 
 	might_sleep();
 
@@ -570,7 +570,6 @@ int sta_info_insert_rcu(struct sta_info *sta) __acquires(RCU)
 
 	return 0;
  out_free:
-	BUG_ON(!err);
 	sta_info_free(local, sta);
 	return err;
 }