mlxsw: Use Switch Multicast ID Register Version 2

The SMID-V2 register maps Multicast ID (MID) into a list of local ports.
It is a new version of SMID in order to support 1024 bits of local_port.

Add SMID-V2 register and use it instead of SMID.

Signed-off-by: Amit Cohen <amcohen@nvidia.com>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>