switchdev: Add extack argument to call_switchdev_notifiers()

A follow-up patch will enable vetoing of FDB entries. Make it possible
to communicate details of why an FDB entry is not acceptable back to the
user.

Signed-off-by: Petr Machata <petrm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/switchdev/switchdev.c b/net/switchdev/switchdev.c
index 5df9d113..cd78253 100644
--- a/net/switchdev/switchdev.c
+++ b/net/switchdev/switchdev.c
@@ -556,10 +556,11 @@ EXPORT_SYMBOL_GPL(unregister_switchdev_notifier);
  *	Call all network notifier blocks.
  */
 int call_switchdev_notifiers(unsigned long val, struct net_device *dev,
-			     struct switchdev_notifier_info *info)
+			     struct switchdev_notifier_info *info,
+			     struct netlink_ext_ack *extack)
 {
 	info->dev = dev;
-	info->extack = NULL;
+	info->extack = extack;
 	return atomic_notifier_call_chain(&switchdev_notif_chain, val, info);
 }
 EXPORT_SYMBOL_GPL(call_switchdev_notifiers);