net/mlx5: Add support for setting parent of nodes

Introduce `mlx5_esw_devlink_rate_node_parent_set()` to allow assigning
a parent to scheduling nodes.
Implement `mlx5_esw_qos_node_update_parent()` and
`mlx5_esw_qos_node_validate_set_parent()` to enforce constraints on
node reassignment.

Don't allow reassignment of nodes with active rate objects.

Update `esw_qos_node_set_parent()` to handle cases where
the parent is NULL. A NULL parent indicates that the scheduling element
is attached to the root scheduling element, and since only rate nodes
can be connected to the root, this update is now necessary.

Signed-off-by: Carolina Jubran <cjubran@nvidia.com>
Reviewed-by: Cosmin Ratiu <cratiu@nvidia.com>
Reviewed-by: Dragos Tatulea <dtatulea@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://patch.msgid.link/1741642016-44918-5-git-send-email-tariqt@nvidia.com


Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>