i40e/i40evf: Add capability to gather VEB per TC stats

This patch adds capability to update per VEB per TC statistics and dump
it via ethtool. It also adds a structure to hold VEB per TC statistics.
The fields can be filled by reading the GLVEBTC_* counters.

Change-ID: I28b4759b9ab6ad5a61f046a1bc9ef6b16fe31538
Signed-off-by: Neerav Parikh <neerav.parikh@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>