igb: restore EEPROM values of MDICNFG on reset with 82580

On a reset the MDICNFG.Destination and MDICNFG.COM_MDIO
register fields are not restored to the EEPROM default.
This patch modifies the reset code to read the EEPROM
and restore the default values.

Signed-off-by: Nicholas Nunley <nicholas.d.nunley@intel.com>
Tested-by: Jeff Pieper <jeffrey.e.pieper@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>