dsa: add missing net/devlink.h include

devlink functions are in use, so include the related header file.
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/dsa/dsa2.c

@@ -18,6 +18,7 @@
 #include <linux/rtnetlink.h>
 #include <linux/of.h>
 #include <linux/of_net.h>
+#include <net/devlink.h>
 
 #include "dsa_priv.h"