i40e: don't handle VF reset on unload

Set the DOWN flag before attempting to disable VFs when unloading the
driver. Also, don't attempt to reset the VFs when the driver is
unloading, because the switch configuration will fail. This fixes a
panic on unload when VFs are enabled.

Change-ID: I25a6567e89c9687145f510ff4f630932412c5c5d
Signed-off-by: Mitch Williams <mitch.a.williams@intel.com>
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Sibai Li <sibai.li@intel.com>
Signed-off-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>