mlxsw: spectrum_switchdev: Disable mdb when mc is disabled

Remove all the mdb entries from the HW when mc is being disabled and
re-write them when it is being enabled.

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>