Add missing PSA_ASSERT in mbedtls_test_psa_raw_key_agreement_with_self

Signed-off-by: Ryan Everett <ryan.everett@arm.com>
diff --git a/tests/src/psa_exercise_key.c b/tests/src/psa_exercise_key.c
index 5aed683..937bd45 100644
--- a/tests/src/psa_exercise_key.c
+++ b/tests/src/psa_exercise_key.c
@@ -715,6 +715,7 @@
         status = PSA_SUCCESS;
         goto exit;
     }
+    PSA_ASSERT(status);
 
     status = psa_raw_key_agreement(alg, key,
                                    public_key, public_key_length,