RDMA/mlx5: Add missing check for return value in get namespace flow

Add missing check for return value when calling to
mlx5_ib_ft_type_to_namespace, even though it can't really fail in this
specific call.

Fixes: 52438be ("RDMA/mlx5: Allow inserting a steering rule to the FDB")
Link: https://lore.kernel.org/r/7b9ceda217d9368a51dc47a46b769bad4af9ac92.1659256069.git.leonro@nvidia.com
Reviewed-by: Itay Aveksis <itayav@nvidia.com>
Signed-off-by: Maor Gottlieb <maorg@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/hw/mlx5/fs.c

@@ -2078,12 +2078,10 @@ static int mlx5_ib_matcher_ns(struct uverbs_attr_bundle *attrs,
 		if (err)
 			return err;
 
-		if (flags) {
-			mlx5_ib_ft_type_to_namespace(
+		if (flags)
+			return mlx5_ib_ft_type_to_namespace(
 				MLX5_IB_UAPI_FLOW_TABLE_TYPE_NIC_TX,
 				&obj->ns_type);
-			return 0;
-		}
 	}
 
 	obj->ns_type = MLX5_FLOW_NAMESPACE_BYPASS;