gtp: switch to dev_get_tstats64

Replace ip_tunnel_get_stats64() with the new identical core function
dev_get_tstats64().
Acked-by: Harald Welte <laforge@gnumonks.org>
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/gtp.c

@@ -607,7 +607,7 @@ static const struct net_device_ops gtp_netdev_ops = {
 	.ndo_init		= gtp_dev_init,
 	.ndo_uninit		= gtp_dev_uninit,
 	.ndo_start_xmit		= gtp_dev_xmit,
-	.ndo_get_stats64	= ip_tunnel_get_stats64,
+	.ndo_get_stats64	= dev_get_tstats64,
 };
 
 static void gtp_link_setup(struct net_device *dev)