mlxsw: spectrum_router: Add multicast routes notification handling functionality

Add functionality for calling the multicast routing offloading logic upon
MFC and VIF add and delete notifications. In addition, call the multicast
routing upon RIF addition and deletion events.

As the multicast routing offload logic may sleep, the actual calls are done
in a deferred work. To ensure the MFC object is not freed in that interval,
a reference is held to it. In case of a failure, the abort mechanism is
used, which ejects all the routes from the hardware and triggers the
traffic to flow through the kernel.

Note: At that stage, the FIB notifications are still ignored, and will be
enabled in a further patch.

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>