mlxsw: spectrum_switchdev: Flood all mc packets to mrouter ports

When mc is enabled, whenever a mc packet doesn't hit any mdb entry it is
being flood to the ports marked as mrouters. However, all mc packets should
be flooded to them even if they match an entry in the mdb.
This patch adds the mrouter ports to every mdb entry that is being written
to the HW.

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>