mscc: Configured MAC entries should be locked.

The MAC table in Ocelot supports auto aging (normal) and static entries.
MAC entries that is manually configured should be static and not subject
to aging.

Fixes: a556c76a ("net: mscc: Add initial Ocelot switch support")
Signed-off-by: Allan Nielsen <allan.nielsen@microchip.com>
Reviewed-by: Steen Hegelund <steen.hegelund@microchip.com>
Signed-off-by: Steen Hegelund <steen.hegelund@microchip.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>