selftests: drv-net: Add test for devlink-rate traffic class bandwidth distribution

selftests: drv-net: Add test for devlink-rate traffic class bandwidth distribution

This test suite validates the functionality of the devlink-rate API for
traffic class (TC) bandwidth allocation. It ensures that bandwidth can
be distributed between different traffic classes as configured, and
verifies that explicit TC-to-queue mapping is required for the
allocation to be effective.

The first test (test_no_tc_mapping_bandwidth) is marked as expected
failure on mlx5, since the hardware automatically enforces traffic
class separation by dynamically moving queues to the correct TC
scheduler, even without explicit TC-to-queue mapping configuration.

Test output on mlx5:
 1..2
 # Created VF interface: eth5
 # Created VLAN eth5.101 on eth5 with tc 3 and IP 198.51.100.2
 # Created VLAN eth5.102 on eth5 with tc 4 and IP 198.51.100.10
 # Set representor eth4 up and added to bridge
 # Bandwidth check results without TC mapping:
 # TC 3: 0.19 Gbits/sec
 # TC 4: 0.76 Gbits/sec
 # Total bandwidth: 0.95 Gbits/sec
 # TC 3 percentage: 20.0%
 # TC 4 percentage: 80.0%
 ok 1 devlink_rate_tc_bw.test_no_tc_mapping_bandwidth # XFAIL Bandwidth matched 80/20 split without TC mapping
 # Created VF interface: eth5
 # Created VLAN eth5.101 on eth5 with tc 3 and IP 198.51.100.2
 # Created VLAN eth5.102 on eth5 with tc 4 and IP 198.51.100.10
 # Set representor eth4 up and added to bridge
 # Bandwidth check results with TC mapping:
 # TC 3: 0.21 Gbits/sec
 # TC 4: 0.78 Gbits/sec
 # Total bandwidth: 0.98 Gbits/sec
 # TC 3 percentage: 21.1%
 # TC 4 percentage: 78.9%
 # Bandwidth is distributed as 80/20 with TC mapping
 ok 2 devlink_rate_tc_bw.test_tc_mapping_bandwidth
 # Totals: pass:1 fail:0 xfail:1 xpass:0 skip:0 error:0

Signed-off-by: Carolina Jubran <cjubran@nvidia.com>
Reviewed-by: Cosmin Ratiu <cratiu@nvidia.com>
Reviewed-by: Nimrod Oren <noren@nvidia.com>
Signed-off-by: Mark Bloch <mbloch@nvidia.com>
Link: https://patch.msgid.link/20250629142138.361537-9-mbloch@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>