mlxsw: spectrum_fid: Configure egress VID classification for multicast

The device includes two main tables to support layer 2 multicast (i.e.,
MDB and flooding). These are the PGT (Port Group Table) table and the MPE
(Multicast Port Egress) table.
- PGT is {MID -> (bitmap of local_port, SPME index)}
- MPE is {(Local port, SMPE index) -> eVID}

In the legacy model, software did not interact with MPE table as it was
completely hidden in firmware. In the new model, software needs to
populate the table itself in order to map from {Local port, SMPE} to an
egress VID. This is done using the SMPE register.

Configure SMPE register when a {Local port, VID} are mapped/unmapped to a
802.1d and 802.1q emulated FIDs. The MPE table is not relevant for rFIDs as
firmware handles their flooding.

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: Paolo Abeni <pabeni@redhat.com>