Add changelog

Signed-off-by: Janos Follath <janos.follath@arm.com>
diff --git a/ChangeLog.d/fix-rsa-performance-regression.txt b/ChangeLog.d/fix-rsa-performance-regression.txt
new file mode 100644
index 0000000..abcc7a5
--- /dev/null
+++ b/ChangeLog.d/fix-rsa-performance-regression.txt
@@ -0,0 +1,2 @@
+Bugfix
+   * Fix unintended performance regression when using short RSA public keys. See #9232.