net/mlx5: E-switch, Introduce rate limiting groups API

Extend eswitch API with rate limiting groups:

- Define new struct mlx5_esw_rate_group that is used to hold all
  internal group data.

- Implement functions that allow creation, destruction and cleanup of
  groups.

- Assign all vports to internal unlimited zero group by default.

This commit lays the groundwork for group rate limiting by implementing
devlink_ops->rate_node_{new|del}() callbacks to support creating and
deleting groups through devlink rate node objects. APIs that allows
setting rates and adding/removing members are implemented in following
patches.

Co-developed-by: Vlad Buslov <vladbu@nvidia.com>
Signed-off-by: Vlad Buslov <vladbu@nvidia.com>
Signed-off-by: Dmytro Linkin <dlinkin@nvidia.com>
Reviewed-by: Huy Nguyen <huyn@nvidia.com>
Reviewed-by: Mark Bloch <mbloch@nvidia.com>
Reviewed-by: Parav Pandit <parav@nvidia.com>
Reviewed-by: Saeed Mahameed <saeedm@nvidia.com>

include/linux/mlx5/mlx5_ifc.h

@@ -865,7 +865,8 @@ struct mlx5_ifc_qos_cap_bits {
 	u8         nic_bw_share[0x1];
 	u8         nic_rate_limit[0x1];
 	u8         packet_pacing_uid[0x1];
-	u8         reserved_at_c[0x14];
+	u8         log_esw_max_sched_depth[0x4];
+	u8         reserved_at_10[0x10];
 
 	u8         reserved_at_20[0xb];
 	u8         log_max_qos_nic_queue_group[0x5];