[doc] Add D2S as valid entry in dashboard script

Signed-off-by: Michael Schaffner <msf@opentitan.org>
diff --git a/util/dashboard/gen_dashboard_entry.py b/util/dashboard/gen_dashboard_entry.py
index 614e877..5e7da50 100644
--- a/util/dashboard/gen_dashboard_entry.py
+++ b/util/dashboard/gen_dashboard_entry.py
@@ -32,6 +32,7 @@
     'D0': 'Initial Work',
     'D1': 'Functional',
     'D2': 'Feature Complete',
+    'D2S': 'Security Countermeasures Complete',
     'D3': 'Design Complete',
     # Verification Stages
     'V0': 'Initial Work',