net/mlx5: fix encap/decap limit for hairpin flow split

net/mlx5: fix encap/decap limit for hairpin flow split

The rte_flow_item_eth and rte_flow_item_vlan items are refined.
The structs do not exactly represent the packet bits captured on the
wire anymore.
Should use real header instead of the whole struct.

Replace the rte_flow_item_* with the existing corresponding rte_*_hdr.

Fixes: 09315fc83861 ("ethdev: add VLAN attributes to ethernet and VLAN items")
Fixes: f9210259cac7 ("net/mlx5: fix raw encap/decap limit")
Signed-off-by: Xiaoyu Min <jackmin@nvidia.com>
Acked-by: Matan Azrad <matan@nvidia.com>