Add conf parameter to mbedtls_ssl_handshake_free

This function is declared in ssl_internal.h, so this is not a public
API change.

This is in preparation for mbedtls_ssl_handshake_free needing to call
methods from the config structure.
diff --git a/include/mbedtls/ssl_internal.h b/include/mbedtls/ssl_internal.h
index 756360b..f990243 100644
--- a/include/mbedtls/ssl_internal.h
+++ b/include/mbedtls/ssl_internal.h
@@ -385,9 +385,11 @@
  * \brief           Free referenced items in an SSL handshake context and clear
  *                  memory
  *
+ * \param conf      SSL configuration
  * \param handshake SSL handshake context
  */
-void mbedtls_ssl_handshake_free( mbedtls_ssl_handshake_params *handshake );
+void mbedtls_ssl_handshake_free( const mbedtls_ssl_config *conf,
+                                 mbedtls_ssl_handshake_params *handshake );
 
 int mbedtls_ssl_handshake_client_step( mbedtls_ssl_context *ssl );
 int mbedtls_ssl_handshake_server_step( mbedtls_ssl_context *ssl );