e1000e: avoid polling h/w registers during link negotiation

Avoid touching hardware registers when possible, otherwise link negotiation
can get messed up when user-level scripts are rapidly polling the driver to
see if/when link is up.  Use the saved link state information instead when
possible.

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>