fix cpplint error

kexinzhao · kexinzhao · commit 9ba36604d845 · 2018-04-03T17:58:50.000-07:00
diff --git a/paddle/fluid/platform/dynload/cudnn.h b/paddle/fluid/platform/dynload/cudnn.h
@@ -16,6 +16,7 @@ limitations under the License. */
 
 #include <cudnn.h>
 #include <dlfcn.h>
+#include <mutex>  // NOLINT
 #include "paddle/fluid/platform/dynload/dynamic_loader.h"
 
 namespace paddle {
