bridge: netlink: add fdb flush

Simple attribute that flushes the bridge's fdb.

Signed-off-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
index a05a430..5853c57 100644
--- a/net/bridge/br_netlink.c
+++ b/net/bridge/br_netlink.c
@@ -859,6 +859,9 @@
 		br_recalculate_fwd_mask(br);
 	}
 
+	if (data[IFLA_BR_FDB_FLUSH])
+		br_fdb_flush(br);
+
 	return 0;
 }