Add ChangeLog for potential overread with USE_PSA

The issue was fixed while adding support for static ECDH with Opaque
keys: https://github.com/Mbed-TLS/mbedtls/pull/5624

This is just adding the ChangeLog entry for that fix.

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
diff --git a/ChangeLog.d/buf-overread-use-psa-static-ecdh.txt b/ChangeLog.d/buf-overread-use-psa-static-ecdh.txt
new file mode 100644
index 0000000..7eff12a
--- /dev/null
+++ b/ChangeLog.d/buf-overread-use-psa-static-ecdh.txt
@@ -0,0 +1,7 @@
+Security
+   * Fix a potential heap buffer overread in TLS 1.2 server-side when
+     MBEDTLS_USE_PSA_CRYPTO is enabled, an opaque key (created with
+     mbedtls_pk_setup_opaque()) is provisioned, and a static ECDH ciphersuite
+     is selected. This may result in an application crash. No path to
+     information leak has been identified.
+