Add ChangeLog entry for ssl serialization bitflags

Signed-off-by: David Horstmann <david.horstmann@arm.com>
diff --git a/ChangeLog.d/fix-ssl-session-serialization-config.txt b/ChangeLog.d/fix-ssl-session-serialization-config.txt
new file mode 100644
index 0000000..ca1cc81
--- /dev/null
+++ b/ChangeLog.d/fix-ssl-session-serialization-config.txt
@@ -0,0 +1,4 @@
+Bugfix
+   * Fix missing bitflags in SSL session serialization headers. Their absence
+     allowed SSL sessions saved in one configuration to be loaded in a
+     different, incompatible configuration.