net/mlx5: check attr pointer validity before dereferencing it

Fix attr pointer validity checks after it was already
dereferenced.

Fixes: cb0d54cb ("net/mlx5e: Fix wrong source vport matching on tunnel rule")
Signed-off-by: Ariel Levkovich <lariel@nvidia.com>
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

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

@@ -143,7 +143,7 @@ mlx5_eswitch_set_rule_source_port(struct mlx5_eswitch *esw,
 		if (mlx5_esw_indir_table_decap_vport(attr))
 			vport = mlx5_esw_indir_table_decap_vport(attr);
 
-		if (attr && !attr->chain && esw_attr->int_port)
+		if (!attr->chain && esw_attr && esw_attr->int_port)
 			metadata =
 				mlx5e_tc_int_port_get_metadata_for_match(esw_attr->int_port);
 		else