mac80211: convert ops checks to WARN_ON

There's no need to BUG_ON when a driver registers
invalid operations, warn and return an error.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/main.c

@@ -545,6 +545,11 @@ struct ieee80211_hw *ieee80211_alloc_hw(size_t priv_data_len,
 	int priv_size, i;
 	struct wiphy *wiphy;
 
+	if (WARN_ON(!ops->tx || !ops->start || !ops->stop || !ops->config ||
+		    !ops->add_interface || !ops->remove_interface ||
+		    !ops->configure_filter))
+		return NULL;
+
 	if (WARN_ON(ops->sta_state && (ops->sta_add || ops->sta_remove)))
 		return NULL;
 
@@ -597,13 +602,6 @@ struct ieee80211_hw *ieee80211_alloc_hw(size_t priv_data_len,
 
 	local->hw.priv = (char *)local + ALIGN(sizeof(*local), NETDEV_ALIGN);
 
-	BUG_ON(!ops->tx);
-	BUG_ON(!ops->start);
-	BUG_ON(!ops->stop);
-	BUG_ON(!ops->config);
-	BUG_ON(!ops->add_interface);
-	BUG_ON(!ops->remove_interface);
-	BUG_ON(!ops->configure_filter);
 	local->ops = ops;
 
 	/* set up some defaults */