Fix some dependencies and warnings in small config
diff --git a/include/polarssl/ssl.h b/include/polarssl/ssl.h
index fa313f4..d9e98a4 100644
--- a/include/polarssl/ssl.h
+++ b/include/polarssl/ssl.h
@@ -954,6 +954,7 @@
                                        int major, int minor );
 
 #if defined(POLARSSL_X509_CRT_PARSE_C)
+#if defined(POLARSSL_X509_CRL_PARSE_C)
 /**
  * \brief          Set the data required to verify peer certificate
  *
@@ -964,6 +965,7 @@
  */
 void ssl_set_ca_chain( ssl_context *ssl, x509_crt *ca_chain,
                        x509_crl *ca_crl, const char *peer_cn );
+#endif /* POLARSSL_X509_CRL_PARSE_C */
 
 /**
  * \brief          Set own certificate chain and private key