app/testpmd: fix protocol size for copy

app/testpmd: fix protocol size for copy

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 so set raw_encap/decap commands should only copy 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")

Signed-off-by: Xiaoyu Min <jackmin@nvidia.com>
Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>