net: dsa: sja1105: add configuration of port policers

This adds partial configuration support for the L2 Policing Table. Out
of the 45 policing entries, only 5 are used (one for each port), in a
shared manner. All 8 traffic classes, and the broadcast policer, are
redirected to a common instance which belongs to the ingress port.

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