ixgbe: Add X552 XFI backplane support

This patch add support for X552 XFI backplane interface.  The XFI
backplane requires a custom tuned link.  HW/FW owns the link config
for XF backplane and SW must not interfere with it.

Signed-off-by: Don Skidmore <donald.c.skidmore@intel.com>
Tested-by: Krishneil Singh <krishneil.k.singh@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>