Update changelog to cover #4246 and #4158

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/ChangeLog b/ChangeLog
index dc03d48..042c257 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -303,6 +303,10 @@
      directly, which is no longer supported.
    * Implement psa_mac_compute() and psa_mac_verify() as defined in the
      PSA Cryptograpy API 1.0.0 specification.
+   * Introduce PSA_WANT_ECC_XXX for ECC curves, and PSA_WANT_CCM/GCM/CMAC,
+     which are used to decide at build time which cryptographic mechanisms to
+     include in the PSA Cryptography interface. For more information, please see
+     (https://github.com/ARMmbed/mbedtls/blob/development/docs/proposed/psa-conditional-inclusion-c.md).
 
 Security
 * Fix a bias in the generation of finite-field Diffie-Hellman-Merkle (DHM)