i40evf: Use net_device_stats from struct net_device

i40evf: Use net_device_stats from struct net_device

Instead of using a private copy of struct net_device_stats in
struct i40evf_adapter, use stats from struct net_device. Also remove the
now unnecessary .ndo_get_stats function.

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Orabug: 26785018
(cherry picked from commit 4a0a3abfd951943f770f5306d32f8640f55568c4)
Signed-off-by: Jack Vogel <jack.vogel@oracle.com>
Reviewed-by: Kyle Fortin <kyle.fortin@oracle.com>