Use correct test case conditionals for helper functions in tests/suites

Fix unused-function errors.

Signed-off-by: Michael Schuster <michael@schuster.ms>
diff --git a/tests/suites/test_suite_psa_crypto.function b/tests/suites/test_suite_psa_crypto.function
index 3841ac6..b805248 100644
--- a/tests/suites/test_suite_psa_crypto.function
+++ b/tests/suites/test_suite_psa_crypto.function
@@ -1316,6 +1316,7 @@
 
 #if defined(MBEDTLS_THREADING_PTHREAD)
 
+#if defined(MBEDTLS_PSA_CRYPTO_STORAGE_C)
 typedef struct same_key_context {
     data_t *data;
     mbedtls_svc_key_id_t key;
@@ -1434,6 +1435,7 @@
 exit:
     return NULL;
 }
+#endif /* MBEDTLS_PSA_CRYPTO_STORAGE_C */
 
 typedef struct generate_key_context {
     psa_key_type_t type;