mlxsw: spectrum_switchdev: Don't write mids to the HW when mc is disabled

Don't write multicast related data to the HW when mc is disabled.
Also, don't allocate mid id to new mids (so the remove function could know
that they weren't wrote 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>