dpaa2-switch: add a prefix to HW ethtool stats

In the next patch, we'll add support for also exporting the MAC
statistics in the ethtool stats. Annotate already present HW stats with
a suggestive prefix.

Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>