ixgbe: Create separate media type for CX4 adapters

Currently the media type detection for CX4 adapters lumps them into a
type of fiber.  This causes some strange fallout when firmware verification
is done on the NIC, and certain fiber NIC rules get enforced incorrectly.

This patch introduces a new media type for CX4, and puts both 82598 and
82599 CX4 adapters into this bucket.

Signed-off-by: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: Don Skidmore <donald.c.skidmore@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>