vlan: Add support for net_devices_ops.ndo_fcoe_enable/_disable to VLAN

This adds implementation of the net_devices_ops.ndo_fcoe_enable/_disable to
the VLAN driver. It checks if the real_dev has support for ndo_fcoe_enable/
ndo_fcoe_disable and if so, passes on to call the associated real_dev.

Signed-off-by: Yi Zou <yi.zou@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>