ixgbe: fix regression on some 82598 adapters

The change to check the SFP+ module again on open() was
causing the XFP (non-SFP+) adapters to be rejected. We
only want to try and re-identify the SFP+ module if the
original probe found that this device was an SFP+ device.
So for this code path (driver loaded with SFP module, module
inserted, ifconfig up of the device) the type will be
ixgbe_phy_unknown for an unidentified SFP+ module.  So we
only check if that is the case.

This problem also shows up on Copper devices.

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