ixgbe: add define for X557 PHY ID

Add a define for the new PHY identification as well as it's mapping
to the correct PHY type.  Also allow ethtool to identify this type
as well.

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>