changelog: fix description for ECDH changes

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/ChangeLog.d/driver-only-ecdh.txt b/ChangeLog.d/driver-only-ecdh.txt
index a360f8f..1aeed64 100644
--- a/ChangeLog.d/driver-only-ecdh.txt
+++ b/ChangeLog.d/driver-only-ecdh.txt
@@ -1,4 +1,7 @@
 Features
    * When a PSA driver for ECDH is present, it is now possible to disable
-     MBEDTLS_ECDH_C in the build in order to save code size. For PK, X.509
-     and TLS to fully work, this requires MBEDTLS_USE_PSA_CRYPTO to be enabled.
+     MBEDTLS_ECDH_C in the build in order to save code size. For TLS 1.2
+     key exchanges based on ECDH(E) to work, this requires
+     MBEDTLS_USE_PSA_CRYPTO. Restartable/interruptible ECDHE operations in
+     TLS 1.2 (ECDHE-ECDSA key exchange) are not supported in those builds yet,
+     as PSA does not have an API for restartable ECDH yet.