Update ChangeLog for ECC.BN EPIC

Actually not much to change there, from a high level perspective things are
quite simple: you used to be able to disable ECP_C, now you can disable
BIGNUM_C too.

There will be more to update in driver-only-build.md which is the right
place for a more detailed explanation of the limitations.

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
diff --git a/ChangeLog.d/driver-only-ecc.txt b/ChangeLog.d/driver-only-ecc.txt
index df70ca1..8878085 100644
--- a/ChangeLog.d/driver-only-ecc.txt
+++ b/ChangeLog.d/driver-only-ecc.txt
@@ -6,8 +6,10 @@
      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.
    * When all of ECDH, ECDSA and EC J-PAKE are either disabled or provided by
-     a driver, it is possible to disable MBEDTLS_ECP_C and still get support
-     for ECC keys and algorithms in PSA. See docs/driver-only-builds.txt.
+     a driver, it is possible to disable MBEDTLS_ECP_C (and MBEDTLS_BIGNUM_C
+     if not required by another module) and still get support for ECC keys and
+     algorithms in PSA, with some limitations. See docs/driver-only-builds.txt
+     for details.
 API changes
    * Mbed TLS 3.4 introduced support for omitting the built-in implementation
      of ECDSA and/or EC J-PAKE when those are provided by a driver. However,