pch_gbe: Omit private ndo_get_stats function

pch_gbe_get_stats() just returns dev->stats so we can leave it out
altogether and let dev_get_stats() do the job.

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>