ssl_tls: Enable Suite B with subset of ECP curves

Make sure the code compiles even if some curves are not defined.

Fixes #1591

ChangeLog

diff --git a/ChangeLog b/ChangeLog
index 7e91900..bca38b5 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -70,6 +70,8 @@
    * Fix Visual Studio Release x64 build configuration by inheriting
      PlatformToolset from the project configuration. Fixes #1430 reported by
      irwir.
+   * Enable Suite B with subset of ECP curves. Make sure the code compiles even
+     if some curves are not defined. Fixes #1591 reported by dbedev.
 
 API Changes
    * Extend the MBEDTLS_SSL_EXPORT_KEYS to export the handshake randbytes,