i40e: priv flag for controlling VEB stats

Add an ethtool priv flag to enable and disable printing
the VEB statistics.

Change-ID: I7654054a3a73b08aa8310d94ee8fce6219107dd8
Signed-off-by: Shannon Nelson <shannon.nelson@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>