igb: Use the instance of net_device_stats from net_device.

Since net_device has an instance of net_device_stats,
we can remove the instance of this from the adapter structure.

Signed-off-by: Ajit Khaparde <ajitk@serverengines.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --cc drivers/net/igb/igb.h
Simple merge

diff --cc drivers/net/igb/igb_ethtool.c
Simple merge

diff --cc drivers/net/igb/igb_main.c
Simple merge