ixgbe: Add support for using FCoE DDP in 82599 as FCoE targets

The FCoE DDP in 82599 can be used for both FCoE initiator as well as FCoE
target, depending on the indication of the exchange being the responder or
originator in the F_CTL (frame control) field in the encapsulated Fiber
Channel frame header (T10 Spec., FC-FS). For the initiator, OX_ID is used
for FCoE DDP, where for the target RX_ID is used for FCoE DDP.

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>