mlxsw: Configure ingress RIF classification

Before layer 2 forwarding, the device classifies an incoming packet to
a FID. The classification is done based on one of the following keys:

1. FID
2. VNI (after decapsulation)
3. VID / {Port, VID}

After classification, the FID is known, but also all the attributes of
the FID, such as the router interface (RIF) via which a packet that
needs to be routed will ingress the router block.

In the legacy model, when a RIF was created / destroyed, it was
firmware's responsibility to update it in the previously mentioned FID
classification records. In the unified bridge model, this responsibility
moved to software.

The third classification requires to iterate over the FID's {Port, VID}
list and issue SVFA write with the correct mapping table according to the
port's mode (virtual or not). We never map multiple VLANs to the same FID
using VID->FID mapping, so such a mapping needs to be performed once.

When a new FID classification entry is configured and the FID already has
a RIF, set the RIF as part of SVFA configuration.

The reverse needs to be done when clearing a RIF from a FID. Currently,
clearing is done by issuing mlxsw_sp_fid_rif_set() with a NULL RIF pointer.
Instead, introduce mlxsw_sp_fid_rif_unset().

Note that mlxsw_sp_fid_rif_set() is called after the RIF is fully
operational, so it conforms to the internal requirement regarding
SVFA.irif_v: "Must not be set for a non-enabled RIF".

Do not set the ingress RIF for rFIDs, as the {Port, VID}->rFID entry is
configured by firmware when legacy model is used, a next patch will
handle this configuration for rFIDs and unified bridge model.

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>