net: mscc: ocelot: initialize list of multicast addresses in common code

This is just common path code that belongs to ocelot_init,
it has nothing to do with a specific SoC/board instance.

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