ibmveth: fix kobj_to_dev.cocci warnings

Use kobj_to_dev() instead of container_of()

Generated by: scripts/coccinelle/api/kobj_to_dev.cocci

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Acked-by: Lijun Pan <lijunp213@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>