e1000e: bad state after running ethtool diagnostics with AMT enabled

When running ethtool online diagnostics with no open interface, there is a
short period of time where the driver relinquishes control of the adapter
during which time AMT (manageability firmware) can put the adapter into an
unknown state resulting in such things as link test failure, hardware hang,
reporting an incorrect link speed, etc.  Resetting the adapter during an
open() resolves this by putting the adapter into a quiescent state.

Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>