Add missing ChangeLog entry

Signed-off-by: Janos Follath <janos.follath@arm.com>
diff --git a/ChangeLog.d/AES_SETKEY_ALT-fix.txt b/ChangeLog.d/AES_SETKEY_ALT-fix.txt
new file mode 100644
index 0000000..2a23fbc
--- /dev/null
+++ b/ChangeLog.d/AES_SETKEY_ALT-fix.txt
@@ -0,0 +1,5 @@
+Bugfix
+   * Fix an issue that occurred when building with MBEDTLS_AES_SETKEY_DEC_ALT.
+     Key management methods that are required for MBEDTLS_CIPHER_MODE_XTS were
+     excluded from the build and led to failure. Fixes #3818. Reported by
+     John Stroebel.