e1000e: enable forced master/slave on 82577

Like other supported (igp) PHYs, the driver needs to be able to force the
master/slave mode on 82577.  Since the code is the same as what already
exists in the code flow for igp PHYs, move it to a new function to be
called for both flows.

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>