igb: Add media switching feature for i354 PHY's

This patch adds a new feature which is supported in some PHY's on some i354
devices.  This feature is Auto Media Detect and allows which ever media is
detected first by the PHY to be the media used and configured by the
device.  This is a media swapping feature that is wholly contained in the
Marvell PHY.

Signed-off-by: Carolyn Wyborny <carolyn.wyborny@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>