selftests: mlxsw: Add ingress RIF configuration test for 802.1D bridge

Before layer 2 forwarding, the device classifies an incoming packet to a
FID. 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.

For VLAN-unaware bridges (802.1D), the FID classification is done according
to {Port, VID}. When a RIF is added on top of a FID, all the existing
{Port, VID}->FID mappings should be updated by the software with the new
RIF. In addition, when a new mapping is added for FID which already has a
RIF, the correct RIF should be used for it.

Add a test to verify that packets can be routed after {Port, VID}->FID
classification, regardless of the order of the configuration.

 # ./ingress_rif_conf_1d.sh
 TEST: Add RIF for existing {port, VID}->FID mapping                 [ OK ]
 TEST: Add {port, VID}->FID mapping for FID with a RIF               [ OK ]

Signed-off-by: Amit Cohen <amcohen@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>