mlxsw: reg: Configure RIF to forward IPv4 multicast packets by default

Turn on two bits on the Spectrum RIF configuration:
 - IPv4 multicast: when a multicast packet arrives on a RIF, send it to go
   through multicast routes lookup.
 - IPv4 multicast forwarding enable: when multicast packet arrives on a
   RIF, allow it to be forwarded by multicast routes. If this bit is not
   set, multicast packets will go through multicast routing lookup but will
   be dropped at the egress of the ports.

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