mlxsw: Configure egress VID for unicast FDB entries

Using unified bridge model, firmware no longer configures the egress VID
"under the hood" and moves this responsibility to software.

For layer 2, this means that software needs to determine the egress VID
for both unicast (i.e., FDB) and multicast (i.e., MDB and flooding) flows.

Unicast FDB records and unicast LAG FDB records have new fields - "set_vid"
and "vid", set them. For records which point to router port, do not set
these fields.

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>