vlan: adds fcoe offload related net_device_ops and updates fcoe_ddp_xid field

Adds fcoe offload related net_device_ops functions vlan_dev_fcoe_ddp_setup
and vlan_dev_fcoe_ddp_done, their implementation simply calls real eth device
net_device_ops for FCoE DDP setup and done operations.

Updates VLAN netdev field value for fcoe_ddp_xid from real eth device netdev.

Above changes are required for fcoe DDP offload working on a VLAN interface.

Signed-off-by: Vasu Dev <vasu.dev@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>