net: dsa: sja1105: show more ethtool statistics counters for P/Q/R/S

It looks like the P/Q/R/S series supports some more counters,
generically named "Ethernet statistics counter", which we were not
printing. Add them.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>