net/mlx5: Simplify QoS scheduling element configuration

Simplify the configuration of QoS scheduling elements by removing the
separate functions `esw_qos_node_config` and `esw_qos_vport_config`.

Instead, directly use the existing `esw_qos_sched_elem_config` function
for both nodes and vports.

This unification helps in generalizing operations on scheduling
elements nodes.

Signed-off-by: Carolina Jubran <cjubran@nvidia.com>
Reviewed-by: Cosmin Ratiu <cratiu@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>