hikey: Package factory image from an existing image

Change-Id: I8b7f27990e6740c4237235151c74778fa3101137
Signed-off-by: Dmitry Shmidt <dimitrysh@google.com>
diff --git a/factory-images/README b/factory-images/README
index 2d7ee90..aaa1fb0 100644
--- a/factory-images/README
+++ b/factory-images/README
@@ -6,3 +6,7 @@
 $ cd out/dist/
 $ . ../../device/linaro/hikey/factory-images/generate-factory-images-package.sh
 
+# Package with an existing image
+# First download the image to the android build top directory
+
+$ device/linaro/hikey/factory-images/generate-factory-images-package.sh