i40e: Dump Stats string removed from debugfs help command

Dump Stats string has been removed from functional debugfs
help message. Now it does not show up when we echo command to
debugfs/Fortville queue.

Change-ID: I9333473826b574f1afa6ddb785fd7adfbdcb2884
Signed-off-by: Sravanthi Tangeda <sravanthi.tangeda@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>