Add dummy server name extension paser

Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>
diff --git a/library/ssl_tls13_client.c b/library/ssl_tls13_client.c
index febf441..7b26bbb 100644
--- a/library/ssl_tls13_client.c
+++ b/library/ssl_tls13_client.c
@@ -1895,7 +1895,12 @@
          */
         switch( extension_type )
         {
+            case MBEDTLS_TLS_EXT_SERVERNAME:
+                MBEDTLS_SSL_DEBUG_MSG( 3, ( "found server_name extension" ) );
 
+                /* The server_name extension should be an empty extension */
+
+                break;
             case MBEDTLS_TLS_EXT_SUPPORTED_GROUPS:
                 MBEDTLS_SSL_DEBUG_MSG( 3, ( "found extensions supported groups" ) );
                 break;