i40e: fix unsigned stat widths

Change i40e_update_vsi_stats and struct i40e_vsi to use u64 fields to match
the width of the stats counters in struct i40e_rx_queue_stats.

Update debugfs code to use the correct format specifier for u64.

Fixes: 41c445ff ("i40e: main driver core")
Signed-off-by: Joe Damato <jdamato@fastly.com>
Reported-by: kernel test robot <lkp@intel.com>
Tested-by: Gurucharan G <gurucharanx.g@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>