use mbedtls_ssl_session_init() to init session variable

Use mbedtls_ssl_session_init() to init variable just like
session-family APIs described

Signed-off-by: Benson Liou <benson.liou@sony.com>
diff --git a/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
index 043988f..96f4bb2 100644
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@@ -4669,7 +4669,7 @@
  * \param ssl      The SSL context representing the connection for which to
  *                 to export a session structure for later resumption.
  * \param session  The target structure in which to store the exported session.
- *                 This must have been initialized with mbedtls_ssl_init_session()
+ *                 This must have been initialized with mbedtls_ssl_session_init()
  *                 but otherwise be unused.
  *
  * \note           This function can handle a variety of mechanisms for session