expo: Support highlighting menu items

Expo normally uses a pointer to show the current item. Add support for
highlighting as well, since this makes it easier for the user to see the
current item.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/boot/cedit.c b/boot/cedit.c
index 5481025..8faf230 100644
--- a/boot/cedit.c
+++ b/boot/cedit.c
@@ -126,6 +126,7 @@
 		return log_msg_ret("sid", ret);
 
 	exp->popup = true;
+	exp->show_highlight = true;
 
 	/* This is not supported for now */
 	if (0)