expo: Support rendering multiple lines of text

Use the measurement info to write each line of text separately, thus
respecting word-wrapping and newlines.

Fix up the comment for scene_obj_render() while we are here.

Since a lineedit does not support alignment, add a special case to just
display the text if there is no measurement. This happens assuming the
lineedit is initially empty.

Signed-off-by: Simon Glass <sjg@chromium.org>

boot/bootflow_menu.c

@@ -241,6 +241,10 @@ int bootflow_menu_start(struct bootstd_priv *std, bool text_mode,
 	if (text_mode)
 		expo_set_text_mode(exp, text_mode);
 
+	ret = expo_calc_dims(exp);
+	if (ret)
+		return log_msg_ret("bmd", ret);
+
 	*expp = exp;
 
 	return 0;