fix comment. test=develop

paddle/fluid/operators/batch_norm_op.cu

@@ -79,11 +79,11 @@ class BatchNormKernel<platform::CUDADeviceContext, T>
     // TODO(dengkaipeng): use PERSISTENT mode in training may incur errors
     // in inference period, cuDNN fixed issues on PERSISTENT mode in version
     // 7.0.2, 7.0.4 and 7.3.0, we disable this mode currently.
-/* #if CUDNN_VERSION_MIN(7, 0, 0) */
-/*     mode_ = CUDNN_BATCHNORM_SPATIAL_PERSISTENT; */
-/* #else */
+    // #if CUDNN_VERSION_MIN(7, 0, 0)
+    //     mode_ = CUDNN_BATCHNORM_SPATIAL_PERSISTENT;
+    // #else
     mode_ = CUDNN_BATCHNORM_SPATIAL;
-/* #endif */
+    // #endif
 
     VLOG(3) << "Setting descriptors.";
     std::vector<int> dims;
@@ -309,11 +309,11 @@ class BatchNormGradKernel<platform::CUDADeviceContext, T>
       // TODO(dengkaipeng): use PERSISTENT mode in training may incur errors
       // in inference period, cuDNN fixed issues on PERSISTENT mode in version
       // 7.0.2, 7.0.4 and 7.3.0, we disable this mode currently.
-/* #if CUDNN_VERSION_MIN(7, 0, 0) */
-/*       mode_ = CUDNN_BATCHNORM_SPATIAL_PERSISTENT; */
-/* #else */
+      // #if CUDNN_VERSION_MIN(7, 0, 0)
+      //       mode_ = CUDNN_BATCHNORM_SPATIAL_PERSISTENT;
+      // #else
       mode_ = CUDNN_BATCHNORM_SPATIAL;
-/* #endif */
+      // #endif
 
       CUDNN_ENFORCE(platform::dynload::cudnnSetTensorNdDescriptor(
           data_desc_, CudnnDataType<T>::type,