mlxsw: spectrum_router: Prepare function for router lock introduction

The function de-associates the port-vlan from its router interface
(RIF). It is called both from the netdev notifier block and the inetaddr
notifier block that will soon hold the router lock.

Make sure that router code calls the internal version, as it will
already have the router lock held when the function is called.

Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>