mlxsw: spectrum_router: Add Multicast routing support for Spectrum-2

Add implementation of Spectrum-2 multicast routes for both IPv4 and IPv6 by
using ACL module explicitly.
In Spectrum-2, multicast routes are set as ACL rules, so initialization
takes care of creating dedicated ACL groups and binding them to the
appropriate multicast routing protocol IPv4/IPv6, and afterwards routes
configuration translates to setting explicit ACL rules.

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