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>

include/expo.h

@@ -8,6 +8,7 @@
 #define __EXPO_H
 
 #include <abuf.h>
+#include <alist.h>
 #include <dm/ofnode_decl.h>
 #include <linux/bitops.h>
 #include <linux/list.h>
@@ -296,11 +297,14 @@ struct scene_obj_img {
  * @str_id: ID of the text string to display
  * @font_name: Name of font (allocated by caller)
  * @font_size: Nominal size of font in pixels
+ * @lines: alist of struct vidconsole_mline with a separate record for each
+ *	line of text
  */
 struct scene_txt_generic {
 	uint str_id;
 	const char *font_name;
 	uint font_size;
+	struct alist lines;
 };
 
 /**