Clarify that what we're dropping is pkcs11-helper support

The PKCS11 module does not directly interface with PKCS#11 (also known
as Cryptoki), but with the pkcs11-helper library.
diff --git a/ChangeLog b/ChangeLog
index 12836ed..852bd5b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -3,8 +3,9 @@
 = mbed TLS X.X.X branch released XXXX-XX-XX
 
 New deprecations
-   * Deprecate MBEDTLS_PKCS11_C that enables the wrapper for PKCS#11 smartcard
-     support.
+   * Deprecate for MBEDTLS_PKCS11_C, the wrapper around the pkcs11-helper
+     library which allows TLS authentication to use keys stored in a
+     PKCS#11 token such as a smartcard.
 
 Bugfix
    * Allow loading symlinked certificates. Fixes #3005. Reported and fixed