net/mlx5: update flow devargs handling for future HW

net/mlx5: update flow devargs handling for future HW

SWS (software steering) will be disabled on future hardware generations.
Update the defaults for the dv_flow_en and allow_duplicate_pattern
devargs accordingly.

- Default dv_flow_en devarg value will be chosen based on whether
  NIC supports SW steering and/or HW steering.
- If DV flow is not supported and allow_duplicate_pattern is
  set by the user, forcibly disable it and emit a clear log message.

This change improves reliability by ensuring only valid
configurations are applied, and provides clear feedback to
the user when fallbacks are triggered.

Signed-off-by: Maayan Kashani <mkashani@nvidia.com>
Acked-by: Dariusz Sosnowski <dsosnowski@nvidia.com>