i40evf: use netdev variable in reset task

If we're going to bother initializing a variable to reference it we might
as well use it.

Signed-off-by: Alan Brady <alan.brady@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>