Update changelog

This patch adds explicit wording to state
that Two's complement is the official
supported signed integer representation.

Signed-off-by: Minos Galanakis <minos.galanakis@arm.com>
diff --git a/ChangeLog b/ChangeLog
index ebf8a36..9cffd5d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -488,6 +488,9 @@
      deprecated.
    * PSA_ALG_AEAD_WITH_DEFAULT_TAG_LENGTH and PSA_ALG_AEAD_WITH_TAG_LENGTH
      have been renamed, and the old names deprecated.
+   * Signed magnitude and one's complement implementations for signed integers are
+     are now officially not supported. Two's Complement is the only supported
+     implementation going forward.
 
 Features
    * The PSA crypto subsystem can now use HMAC_DRBG instead of CTR_DRBG.