test/crypto: fix null dereference of crypto op

test/crypto: fix null dereference of crypto op

In two test cases, the op value is set by the return of the
process_crypto_request function, which may be NULL. The op->status
value was checked afterwards, which was causing a dereference issue.

To fix this, a temporary op variable is used to hold the return
from the process_crypto_request function, so the original op->status
can be checked after the possible NULL return value.
The original op value is then set to hold the temporary op value.

Coverity issue: 363452, 363465
Fixes: 4868f6591c6f ("test/crypto: add cases for raw datapath API")

Signed-off-by: Ciara Power <ciara.power@intel.com>
Acked-by: Akhil Goyal <akhil.goyal@nxp.com>