ixgbe: report correct media type for KR, KX and KX4 interfaces

Ethtool reports backplane type interfaces as 1000/10000baseT link modes.
This has been corrected to report the media as KR, KX or KX4 based on the
backplane interface present.

Signed-off-by: Veola Nazareth <veola.nazareth@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>