net/mlx5e: Use IS_ERR() to check and simplify code

Use IS_ERR() and PTR_ERR() instead of PTR_ERR_OR_ZERO() to
simplify code, avoid redundant judgements.

Signed-off-by: Zhang Shengju <zhangshengju@cmss.chinamobile.com>
Signed-off-by: Tang Bin <tangbin@cmss.chinamobile.com>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

drivers/net/ethernet/mellanox/mlx5/core/en/tc_tun.c

@@ -96,9 +96,8 @@ static int mlx5e_route_lookup_ipv4(struct mlx5e_priv *priv,
 	}
 
 	rt = ip_route_output_key(dev_net(mirred_dev), fl4);
-	ret = PTR_ERR_OR_ZERO(rt);
-	if (ret)
-		return ret;
+	if (IS_ERR(rt))
+		return PTR_ERR(rt);
 
 	if (mlx5_lag_is_multipath(mdev) && rt->rt_gw_family != AF_INET) {
 		ip_rt_put(rt);