net/mlx5e: Make function mlx5e_change_rep_mtu() static

Fixes the following sparse warning:

drivers/net/ethernet/mellanox/mlx5/core/en_rep.c:903:5: warning:
 symbol 'mlx5e_change_rep_mtu' was not declared. Should it be static?
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlx5/core/en_rep.c

@@ -900,7 +900,7 @@ static const struct switchdev_ops mlx5e_rep_switchdev_ops = {
 	.switchdev_port_attr_get	= mlx5e_attr_get,
 };
 
-int mlx5e_change_rep_mtu(struct net_device *netdev, int new_mtu)
+static int mlx5e_change_rep_mtu(struct net_device *netdev, int new_mtu)
 {
 	return mlx5e_change_mtu(netdev, new_mtu, NULL);
 }