Add Changelog entry

Signed-off-by: Paul Elliott <paul.elliott@arm.com>
diff --git a/ChangeLog.d/make_base64_table_access_constant_flow.txt b/ChangeLog.d/make_base64_table_access_constant_flow.txt
new file mode 100644
index 0000000..a119389
--- /dev/null
+++ b/ChangeLog.d/make_base64_table_access_constant_flow.txt
@@ -0,0 +1,4 @@
+Security
+   * Guard against strong local side channel attack against base64 tables by
+    making access aceess to them use constant flow code.
+