test: fix TCP header initialization
test: fix TCP header initialization

Initialize TCP data offset field with TCP header length, this
field is used to derive L4 header length and by hardware to
validate a TCP header.

Fixes: 41f72ec94074 ("test: add packet burst generator functions")
Cc: stable@dpdk.org

Signed-off-by: Lance Richardson <4e26776f5588f0e1c0c16cd2ddc0e9efc79c5b3a@broadcom.com>
Reviewed-by: Ferruh Yigit <ba8734c3c506d2e3557bd4ac8fdaccd25bdb9aa7@intel.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk