[SCSI] net: add FCoE offload support through net_device

This adds support to provide Fiber Channel over Ethernet (FCoE) offload
through net_device's net_device_ops struct. The offload through net_device
for FCoE is enabled in kernel as built-in or module driver.

Signed-off-by: Yi Zou <yi.zou@intel.com>
Acked-by: David Miller <davem@davemloft.net>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>