octeon_ep_vf: add ethtool support

Add support for the following ethtool commands:

ethtool -i|--driver devname
ethtool devname
ethtool -S|--statistics devname

Signed-off-by: Shinas Rasheed <srasheed@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>