i40e: report correct statistics when XDP is enabled

When XDP is enabled, the driver will report incorrect
statistics. Received frames will reported as transmitted frames.

This commits fixes the i40e implementation of ndo_get_stats64 (struct
net_device_ops), so that iproute2 will report correct statistics
(e.g. when running "ip -stats link show dev eth0") even when XDP is
enabled.

Reported-by: Jesper Dangaard Brouer <brouer@redhat.com>
Fixes: 74608d17 ("i40e: add support for XDP_TX action")
Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>