i40e: Stop the VF device after setting its MAC address

If the host VMM administrator has changed the VF device's MAC address then
the i40e driver needs to halt the VF device so that the administrator will
be forced to reload the VF driver.  This will cause the VF driver to start
using the newly assigned MAC address.  This brings the i40e driver into
conformance with operational characteristics of other Intel SR-IOV
featured drivers.

Change-ID: Ic7242cceb8287dd2cb72fb1f3166a032a28bf88a
Signed-off-by: Greg Rose <gregory.v.rose@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>