psa: Add backwards compatible error codes

Add deprecated error codes to help transition between the previous
version of the PSA Crypto specification and the current one.
diff --git a/tests/scripts/test_psa_constant_names.py b/tests/scripts/test_psa_constant_names.py
index d22652e..5e128eb 100755
--- a/tests/scripts/test_psa_constant_names.py
+++ b/tests/scripts/test_psa_constant_names.py
@@ -131,11 +131,16 @@
     excluded_name_re = re.compile('_(?:GET|IS|OF)_|_(?:BASE|FLAG|MASK)\Z')
     # Additional excluded macros.
     # PSA_ALG_ECDH and PSA_ALG_FFDH are excluded for now as the script
-    # currently doesn't support them.
+    # currently doesn't support them. Deprecated errors are also excluded.
     excluded_names = set(['PSA_ALG_AEAD_WITH_DEFAULT_TAG_LENGTH',
                           'PSA_ALG_FULL_LENGTH_MAC',
                           'PSA_ALG_ECDH',
-                          'PSA_ALG_FFDH'])
+                          'PSA_ALG_FFDH',
+                          'PSA_ERROR_UNKNOWN_ERROR',
+                          'PSA_ERROR_OCCUPIED_SLOT',
+                          'PSA_ERROR_EMPTY_SLOT',
+                          'PSA_ERROR_INSUFFICIENT_CAPACITY',
+                          ])
     argument_split_re = re.compile(r' *, *')
     def parse_header_line(self, line):
         '''Parse a C header line, looking for "#define PSA_xxx".'''