Fix #ifdefs on ssl_cli.c or ssl_srv.c

Nothing to do with the current branch except I'm going to refine such #ifdefs
for tickets next and I want to start from a clean state
diff --git a/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
index 7609ca9..7235a24 100644
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@@ -1769,7 +1769,7 @@
  * \return         0 if successful
  */
 int mbedtls_ssl_conf_dh_param_ctx( mbedtls_ssl_config *conf, mbedtls_dhm_context *dhm_ctx );
-#endif /* MBEDTLS_DHM_C */
+#endif /* MBEDTLS_DHM_C && defined(MBEDTLS_SSL_SRV_C) */
 
 #if defined(MBEDTLS_SSL_SET_CURVES)
 /**