examples/fips_validation: support scatter gather list

examples/fips_validation: support scatter gather list

This patch adds SGL support to FIPS sample application.
Originally the application allocates single mbuf of 64KB - 1
bytes data room. With the change the user may reduce the
mbuf dataroom size by using the add cmdline option. If the
input test data is longer than the user provided data room
size the application will automatically build chained mbufs
for the target cryptodev PMD to test.

Signed-off-by: Fan Zhang <roy.fan.zhang@intel.com>
Acked-by: John Griffin <john.griffin@intel.com>