i40e: fix stats offsets

The code was setting up stats that were not being initialized.
This caused several counters to be displayed incorrectly, due
to indexing beyond the array of strings when printing stats.

Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>