Update ChangeLog for CCM/GCM improvements

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
diff --git a/ChangeLog.d/driver-only-cipher.txt b/ChangeLog.d/driver-only-cipher.txt
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+++ b/ChangeLog.d/driver-only-cipher.txt
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+Features
+   * If a cipher or AEAD mechanism has a PSA driver, you can now build the
+     library without the corresponding built-in implementation. Generally
+     speaking that requires both the key type and algorithm to be accelerated
+     or they'll both be built in. However for CCM and GCM the built-in
+     implementation is able to take advantage of a driver that only
+     accelerates the key type (that is, the block cipher primitive). See
+     docs/driver-only-builds.md for full details and current limitations.
+   * The CTR_DRBG module will now use AES from a PSA driver if MBEDTLS_AES_C is
+     disabled. This requires PSA_WANT_ALG_ECB_NO_PADDING in addition to
+     MBEDTLS_PSA_CRYPTO_C and PSA_WANT_KEY_TYPE_AES.