Fix README.

Change-Id: Ia16dae237dedceae16be79c6e07fb880e552a6bf
diff --git a/README.md b/README.md
index 6c9f7fb..99b89e9 100644
--- a/README.md
+++ b/README.md
@@ -44,7 +44,7 @@
 - SW-BCM68620_2_4_3_6.zip
 - sdk-all-6.5.7.tar.gz
 - ACCTON_BAL_2.4.3.6-V201710131639.patch
-- OPENOLT_BAL_2.4.3.6.zip
+- OPENOLT_BAL_2.4.3.6.patch
 
 ## Build