net/mlx5e: IPoIB, Fix error handling in mlx5_rdma_netdev_alloc()

The labels were out of order, so it either could result in an Oops or a
leak.

Fixes: 48935bbb ("net/mlx5e: IPoIB, Add netdevice profile skeleton")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>