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>
diff --git a/boot/bootflow_menu.c b/boot/bootflow_menu.c
index 6a37fa8..ab21ed8 100644
--- a/boot/bootflow_menu.c
+++ b/boot/bootflow_menu.c
@@ -241,6 +241,10 @@
 	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;