[SCSI] fcoe, libfc: check offload features from LLD through netdev

This checks if net_devices supports FCoE offload ops in netdev_ops and it
if it does, then sets up the corresponding flags in the associated fc_lport.

For large send offload, the maximum length supported in one large send is now
described by the added lso_max in fc_lport, which is setup initially from
netdev->gso_max_size.

Signed-off-by: Yi Zou <yi.zou@intel.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>