mlxsw: spectrum_switchdev: Remove mrouter flood in mdb flush

In mdb flush the port is being removed from all the mids it is registered
to. But if the port is mrouter, all the mids floods to it.
This patch remove mrouter ports from mids it is not registered to in the
mdb flush.

Signed-off-by: Nogah Frankel <nogahf@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>