app/crypto-perf: fix latency CSV output

app/crypto-perf: fix latency CSV output

The csv output for the latency performance test had an extra header,
"Packet Size", which is a duplicate of "Buffer Size", and had no
corresponding value in the output. This is now removed.

Fixes: f6cefe253cc8 ("app/crypto-perf: add range/list of sizes")
Cc: stable@dpdk.org
Signed-off-by: Ciara Power <ciara.power@intel.com>
Acked-by: Declan Doherty <declan.doherty@intel.com>
Acked-by: Adam Dybkowski <adamx.dybkowski@intel.com>