ixgbe: Add X552 iXFI configuration helper function

X553 doesn't need all the initialization that X552 did for iXFI. This
patch will allow native SPI SFP+ to work with X553 devices.  Future
patches will add additional configuration as needed.

Signed-off-by: Don Skidmore <donald.c.skidmore@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>