examples/fips_validation: remove unused allocation

examples/fips_validation: remove unused allocation

The val.val pointer is allocated memory, however this memory is then
freed in get_writeback_data() without being used beforehand.
The pointer is then allocated memory again before use,
so the very first allocation is removed as it was unnecessary.

Fixes: f4797bae0050 ("examples/fips_validation: support plain SHA")
Cc: stable@dpdk.org
Signed-off-by: Ciara Power <ciara.power@intel.com>
Acked-by: Fan Zhang <roy.fan.zhang@intel.com>