e1000e: 82579 SMBus address and LEDs incorrect after device reset

Since the hardware is prevented from performing automatic PHY configuration
(the driver does it instead), the OEM_WRITE_ENABLE bit in the EXTCNF_CTRL
register will not get cleared preventing the SMBus address and the LED
configuration to be written to the PHY registers.  On 82579, do not check
the OEM_WRITE_ENABLE bit.

Signed-off-by: Bruce Allan <bruce.w.allan@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>