net/mlx5: fix Direct Verbs flow tunnel

net/mlx5: fix Direct 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 distinguish
between outer and inner item. This 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. Dynamic parsing
(item_flags) is added as there's no such code.

2) Refactoring code
- flow_dv_create_item() and flow_dv_create_action() are merged into
  flow_dv_translate() for consistency with Verbs and *_validate().

Fixes: 246636411536 ("net/mlx5: fix flow tunnel handling")
Fixes: d02cb0691299 ("net/mlx5: add Direct Verbs translate actions")
Fixes: fc2c498ccb94 ("net/mlx5: add Direct Verbs translate items")

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