add option to add DSA keys

Change-Id: I200d67e5ca255addd65c9e1bd42ec3c7132d1df7
diff --git a/README.rst b/README.rst
index 2cf834b..a3625c7 100644
--- a/README.rst
+++ b/README.rst
@@ -138,6 +138,14 @@
     #
     # will give you an timeout of 30 minutes (600 sec x 3)
 
+Enable DSA legacy keys:
+
+.. code-block:: yaml
+
+    openssh:
+      server:
+        dss_enabled: true
+
 Read more
 =========