ssl_helpers.c: add mbedtls_test_ssl prefix for *_exchange_data

Signed-off-by: Yanray Wang <yanray.wang@arm.com>
diff --git a/tests/include/test/ssl_helpers.h b/tests/include/test/ssl_helpers.h
index 3090264..6b51950 100644
--- a/tests/include/test/ssl_helpers.h
+++ b/tests/include/test/ssl_helpers.h
@@ -498,10 +498,11 @@
  *
  * \retval  0 on success, otherwise error code.
  */
-int mbedtls_exchange_data(mbedtls_ssl_context *ssl_1,
-                          int msg_len_1, const int expected_fragments_1,
-                          mbedtls_ssl_context *ssl_2,
-                          int msg_len_2, const int expected_fragments_2);
+int mbedtls_test_ssl_exchange_data(
+    mbedtls_ssl_context *ssl_1,
+    int msg_len_1, const int expected_fragments_1,
+    mbedtls_ssl_context *ssl_2,
+    int msg_len_2, const int expected_fragments_2);
 
 #if defined(MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED) && \
     defined(MBEDTLS_CERTS_C) && \