app/testpmd: fix MPLSoGRE encapsulation

app/testpmd: fix MPLSoGRE encapsulation

In function cmd_set_mplsogre_encap_parsed(), MPLS label value was
set in mplsogre_encap_conf struct without the required offset.
As a result the value was copied incorrectly into
rte_flow_item_mpls struct.

This patch sets MPLS label value in appropriate location at
mplsogre_encap_conf struct, so it is correctly copied to
rte_flow_item_mpls struct.

Fixes: 3e77031be855 ("app/testpmd: add MPLSoGRE encapsulation")
Cc: stable@dpdk.org
Signed-off-by: Dekel Peled <dekelp@mellanox.com>
Acked-by: Ori Kam <orika@mellanox.com>