i40evf: free rings in remove function

When the i40evf_remove() calls netdev close, the device doesn't actually
close - it schedules the work for the watchdog to perform. Since we're
stopping the watchdog, this work doesn't get done. However, we're
resetting the part, so we can free resources after the reset request has
gone through. This plugs a memory leak.

Change-ID: Id5335dcaf76ce00d2a4c3d26e9faf711d7f051cf
Signed-off-by: Mitch Williams <mitch.a.williams@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>