e1000e: ethtool unnecessarily takes device out of RPM suspend

A previous patch (commit e60b22c5 e1000e: fix accessing to suspended
device) added .begin and .complete ethtool driver callbacks so that the
device was resumed from Runtime Power Management (RPM) suspend state for
all ethtool operations.  This is overkill for operations which do not need
to access any registers in the device.  This patch makes it so that the
device is taken out of RPM suspend only for those ethtool operations that
must access device registers.

Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>