Improve ChangeLog entry for driver-only hashes

- avoid long unstructured paragraph with long messy sentences
- de-emphasize "no longer depends on MD" and emphasize "can work in
some driver-only builds" instead - that's what users are interested in
(building without MD is just the current way to accomplish that, but
that will change in the future)

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>

ChangeLog.d/driver-only-hashes.txt

@@ -1,24 +1,19 @@
 Features
-   * Some crypto modules that previously depended on MD or a low-level hash
-     module, either unconditionally (RSA, PK, PKCS5, PKCS12, EC J-PAKE), or
-     for some features (PEM for encrypted files), are now able to use PSA
-     Crypto instead when the legacy API is not available. This means it is
-     now possible to use all features from those modules in configurations
-     where the built-in implementations of hashes are excluded and the hashes
-     are only provided by PSA drivers. In these configurations, you need to
-     call `psa_crypto_init()` before you call any function from those
-     modules; this is not required in configurations where the built-in
-     implementation is still available. Note that for modules that use MD
-     (RSA, PKCS5, PKCS12, EC J-PAKE) in builds that have MBEDTLS_MD_C enabled,
-     all hashes used with those modules need to be built-in, as drivers are only
-     used when MBEDTLS_MD_C is disabled; configurations where some hashes are
-     available as built-ins, and some only from drivers, are currently not
-     supported. Also note that some crypto modules and features still depend on
-     the built-in implementation of hashes: MBEDTLS_HKDF_C (but the PSA HKDF
-     functions do not depend on it), MBEDTLS_ENTROPY_C, MBEDTLS_HMAC_DRBG_C and
-     MBEDTLS_ECDSA_DETERMINISTIC. In particular, for now, compiling without
-     built-in hashes requires use of MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG.
-   * When MBEDTLS_USE_PSA_CRYPTO is enabled, X.509, TLS 1.2 and TLS 1.3 no
-     longer depend on MD. This means it is now possible to use them in
-     configurations where the built-in implementations of hashes are excluded
-     and the hashes are only provided by PSA drivers.
+   * Some modules can now use PSA drivers for hashes, including with no
+     built-in implementation present, but only in some configurations.
+     - RSA PKCS#1 v2.1, PKCS5, PKCS12 and EC J-PAKE now use hashes from PSA
+       when (and only when) MBEDTLS_MD_C is disabled.
+     - PEM parsing of encrypted files now uses MD-5 from PSA when (and only
+       when) MBEDTLS_MD5_C is disabled.
+     See the documentation of the corresponding macros in mbedtls_config.h for
+     details.
+     Note that some modules are not able to use hashes from PSA yet, including
+     the entropy module. As a consequence, for now the only way to build with
+     all hashes only provided by drivers (no built-in hash) is to use
+     MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG.
+   * When MBEDTLS_USE_PSA_CRYPTO is enabled, X.509, TLS 1.2 and TLS 1.3 now
+     properly negotiate/accept hashes based on their availability in PSA.
+     As a consequence, they now work in configurations where the built-in
+     implementations of (some) hashes are excluded and those hashes are only
+     provided by PSA drivers. (See previous entry for limitation on RSA-PSS
+     though: that module only use hashes from PSA when MBEDTLS_MD_C is off).