ixgbe: Update NW_MNG_IF_SEL support for X553

The MAC register NW_MNG_IF_SEL fields have been redefined for
X553. These changes impact the iXFI driver code flow. Since iXFI is
only supported in X552, add MAC checks for iXFI flows.

Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Signed-off-by: Paul Greenwalt <paul.greenwalt@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>