net/iavf: fix GTP-U extension flow

net/iavf: fix GTP-U extension flow

Due to the change of struct rte_gtp_psc_generic_hdr, kernel driver can
not handle gtp_psc properly, we introduce a new structure to fix this
gap between kernel driver and struct rte_gtp_psc_generic_hdr.

Fixes: d5eb3e600d9e ("net/iavf: support flow director basic rule")
Cc: stable@dpdk.org
Signed-off-by: Wenxuan Wu <wenxuanx.wu@intel.com>
Tested-by: Zhimin Huang <zhiminx.huang@intel.com>
Acked-by: Qiming Yang <qiming.yang@intel.com>