net/mlx5: fix Verbs flow tunnel

net/mlx5: fix Verbs flow tunnel

1) Fix layer parsing
In translation of tunneled flows, dev_flow->layers must not be used to
check tunneled layer as it contains all the layers parsed from
flow_drv_prepare(). Checking tunneled layer is needed to set
IBV_FLOW_SPEC_INNER and it should be based on dynamic parsing. With
dev_flow->layers on a tunneled flow, items will always be interpreted as
inner as dev_flow->layer already has all the items.

2) Refactoring code
It is partly because flow_verbs_translate_item_*() sets layer flag. Same
code is repeating in multiple locations and that could be error-prone.

- Introduce VERBS_SPEC_INNER() to unify setting IBV_FLOW_SPEC_INNER.
- flow_verbs_translate_item_*() doesn't set parsing result -
  MLX5_FLOW_LAYER_*.
- flow_verbs_translate_item_*() doesn't set priority or adjust hashfields
  but does only item translation. Both have to be done outside.
- Make more consistent between Verbs and DV.

3) Remove flow_verbs_mark_update()
This code can never be reached as validation prohibits specifying mark and
flag actions together. No need to convert flag to mark.

Fixes: 84c406e74524 ("net/mlx5: add flow translate function")

Signed-off-by: Yongseok Koh <yskoh@mellanox.com>
Acked-by: Ori Kam <orika@mellanox.com>