i40e: un-disable VF after reset

When a VF is disabled, there is no way for it to recover until either
the PF driver is reloaded or SR-IOV is disabled and enabled. To correct
this, enable the VF after a successful reset.

Change-ID: I9e0788476c4d53d5407961b503febdfff2b8a7c6
Signed-off-by: Mitch Williams <mitch.a.williams@intel.com>
Tested-by: Jim Young <james.m.young@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>