Allow to configure the stack's behaviour on unexpected CIDs

This commit modifies the CID configuration API mbedtls_ssl_conf_cid_len()
to allow the configuration of the stack's behaviour when receiving an
encrypted DTLS record with unexpected CID.
diff --git a/include/mbedtls/config.h b/include/mbedtls/config.h
index 2e1b982..2ad39db 100644
--- a/include/mbedtls/config.h
+++ b/include/mbedtls/config.h
@@ -1335,7 +1335,7 @@
  * in the underlying transport.
  *
  * Setting this option enables the SSL APIs `mbedtls_ssl_set_cid()`,
- * `mbedtls_ssl_get_peer_cid()` and `mbedtls_ssl_conf_cid_len()`.
+ * `mbedtls_ssl_get_peer_cid()` and `mbedtls_ssl_conf_cid()`.
  * See their documentation for more information.
  *
  * \warning The Connection ID extension is still in draft state.