app/crypto-perf: refactor common test code

Currently, there is some duplication in all the test types,
in the crypto performance application.

In order to improve maintainability of this code,
and ease future work on it, common functions have been separated
in a different file that gets included in all the tests.

Signed-off-by: Pablo de Lara <pablo.de.lara.guarch@intel.com>
Acked-by: Akhil Goyal <akhil.goyal@nxp.com>