More precise recognition of key policy negative tests

The test function asymmetric_signature_key_policy combines positive
and negative tests inside the code, so it doesn't take a status as its
last argument.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/tests/scripts/set_psa_test_dependencies.py b/tests/scripts/set_psa_test_dependencies.py
index 49716b8..ec10387 100755
--- a/tests/scripts/set_psa_test_dependencies.py
+++ b/tests/scripts/set_psa_test_dependencies.py
@@ -164,7 +164,7 @@
     # Run key policy negative tests even if the algorithm to attempt performing
     # is not supported.
     if function_name.endswith('_key_policy') and \
-       arguments[-1] != 'PSA_SUCCESS':
+       arguments[-1].startswith('PSA_ERROR_'):
         arguments[-2] = ''
 
     for arg in arguments: