net: dsa: felix: add port policers

This patch is a trivial passthrough towards the ocelot library, which
support port policers since commit 2c1d029a ("net: mscc: ocelot:
Implement port policers via tc command").

Some data structure conversion between the DSA core and the Ocelot
library is necessary, for policer parameters.

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