net: bridge: add helper to set topology change

Add a __br_set_topology_change helper to set the topology change value.

This can be later extended to add actions when the topology change flag
is set or cleared.

Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/bridge/br_private_stp.h b/net/bridge/br_private_stp.h
index 2fe910c..3f7543a 100644
--- a/net/bridge/br_private_stp.h
+++ b/net/bridge/br_private_stp.h
@@ -61,6 +61,7 @@ void br_received_tcn_bpdu(struct net_bridge_port *p);
 void br_transmit_config(struct net_bridge_port *p);
 void br_transmit_tcn(struct net_bridge *br);
 void br_topology_change_detection(struct net_bridge *br);
+void __br_set_topology_change(struct net_bridge *br, unsigned char val);
 
 /* br_stp_bpdu.c */
 void br_send_config_bpdu(struct net_bridge_port *, struct br_config_bpdu *);