e1000e: power off PHY after reset when interface is down

Some Phys supported by the driver do not remain powered off across a reset
of the device when the interface is down, e.g. on 82571, but not on 82574.
This patch powers down (only when WoL is disabled) the PHY after a reset if
the interface is down and the ethtool diagnostics are not currently running.

The ethtool diagnostic function required a minor re-factor as a result, and
the e1000_[get|put]_hw_control() functions are renamed since they are no
longer static to netdev.c as they are needed by the ethtool diagnostics.
A couple minor whitespace issues were cleaned up, too.

Reported-by: Arthur Jones <ajones@riverbed.com>
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>