RDMA/{core, cma}: Simplify rdma_translate_ip

Since no caller needs vlan, rdma_translate_ip is simplified to avoid
vlan pointer.

Signed-off-by: Parav Pandit <parav@mellanox.com>
Reviewed-by: Daniel Jurgens <danielj@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>