net/mlx5: E-switch, Enable vport QoS on demand

Vports' QoS is not commonly used but consume SW/HW resources, which
becomes an issue on BlueField SoC systems.
Don't enable QoS on vports by default on eswitch mode change and enable
when it's going to be used by one of the top level users:
- configuring TC matchall filter with police action;
- setting rate with legacy NDO API;
- calling devlink ops->rate_leaf_*() callbacks.

Disable vport QoS on vport cleanup.

Signed-off-by: Dmytro Linkin <dlinkin@nvidia.com>
Reviewed-by: Parav Pandit <parav@nvidia.com>
Reviewed-by: Mark Bloch <mbloch@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>