Add support for 'tc-bw' attribute in devlink-rate

Add support for 'tc-bw' attribute in devlink-rate

Introduce a new attribute 'tc-bw' to devlink-rate, allowing users to
set the bandwidth allocation per traffic class. The new attribute
enables fine-grained QoS configurations by assigning relative bandwidth
shares to each traffic class, supporting more precise traffic shaping,
which helps in achieving more precise bandwidth management across
traffic streams.

Add support for configuring 'tc-bw' via the devlink userspace utility
and parse the 'tc-bw' arguments for accurate bandwidth assignment per
traffic class.

This feature supports 8 traffic classes as defined by the IEEE 802.1Qaz
standard.

Example commands:
- devlink port function rate add pci/0000:08:00.0/group \
  tx_share 10Gbit tx_max 50Gbit tc-bw 0:20 1:0 2:0 3:0 4:0 5:80 6:0 7:0

- devlink port function rate set pci/0000:08:00.0/group \
  tc-bw 0:20 1:0 2:0 3:0 4:0 5:80 6:0 7:0

Signed-off-by: Carolina Jubran <cjubran@nvidia.com>
Reviewed-by: Cosmin Ratiu <cratiu@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: David Ahern <dsahern@kernel.org>