ixgbe: add support for disabling link at boot time on 82599

This patch adds support for disabling link during boot time. This
feature was requested by customers and is configurable through the EEPROM.

Signed-off-by: Emil Tantilov <emil.s.tantilov@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>