ixgbe: adds x550 specific FCoE offloads

Adds x550 specific FCoE offloads for DDP context programming and
increased DDP exchanges.

Signed-off-by: Vasu Dev <vasu.dev@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>