cryptodev: fix session init return value

cryptodev: fix session init return value

When calling rte_cryptodev_sym_session_init(),
if there was an error, it returned -1, instead
of returning the specific error code, which can
be valuable for the application for error handling.

Fixes: b3bbd9e5f265 ("cryptodev: support device independent sessions")

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