net: sparx5: add ethtool configuration and statistics support

This adds statistic counters for the network interfaces provided
by the driver.  It also adds CPU port counters (which are not
exposed by ethtool).
This also adds support for configuring the network interface
parameters via ethtool: speed, duplex, aneg etc.

Signed-off-by: Steen Hegelund <steen.hegelund@microchip.com>
Signed-off-by: Bjarni Jonasson <bjarni.jonasson@microchip.com>
Signed-off-by: Lars Povlsen <lars.povlsen@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>