i40e: remove debugfs dump stats

The debugfs dump stats wasn't being kept up-to-date, was redundant with
the ethtool output, and didn't offer any useful additional info.  Rather
than continue trying to keep them aligned, just remove the debugfs command.

Change-ID: Id130ed9aef01c6369ab662c7b4c5ec5b1dbc5b40
Signed-off-by: Shannon Nelson <shannon.nelson@intel.com>
Signed-off-by: Patrick Lu <patrick.lu@intel.com>
Tested-by: Jim Young <Jamesx.m.young@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>