net/mlx5e: Make mlx5e_dcbnl_ops static

Fix sparse warning:
drivers/net/ethernet/mellanox/mlx5/core/en_dcbnl.c:988:29:
error: symbol 'mlx5e_dcbnl_ops' was not declared. Should it be static?
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

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

@@ -985,7 +985,7 @@ static int mlx5e_dcbnl_setbuffer(struct net_device *dev,
 	return err;
 }
 
-const struct dcbnl_rtnl_ops mlx5e_dcbnl_ops = {
+static const struct dcbnl_rtnl_ops mlx5e_dcbnl_ops = {
 	.ieee_getets	= mlx5e_dcbnl_ieee_getets,
 	.ieee_setets	= mlx5e_dcbnl_ieee_setets,
 	.ieee_getmaxrate = mlx5e_dcbnl_ieee_getmaxrate,