fix a bug which will casue cuda address error when the input size is very large (#41824)

As the title

paddle/fluid/operators/gather_scatter_kernel.cu

@@ -119,7 +119,7 @@ struct gpu_gather_scatter_functor {
         is_scatter_like ? self_dims[dim] : src_dims[dim];
     int64_t inner_dim_size = 1;
     int64_t outer_dim_size = 1;
-    for (int64_t i = 0; i < index_dims.size(); ++i) {
+    for (int64_t i = 0; i < dim; ++i) {
       inner_dim_size *= index_dims[i];
     }
 
@@ -127,11 +127,8 @@ struct gpu_gather_scatter_functor {
       outer_dim_size *= index_dims[i];
     }
 
-    int64_t slice_size = 1;
-    for (int i = 1; i < src_dims.size(); ++i) slice_size *= src_dims[i];
-
     int block = 512;
-    int64_t n = slice_size * index_size;
+    int64_t n = inner_dim_size * select_dim_size * outer_dim_size;
     int64_t grid = (n + block - 1) / block;
     auto stream =
         reinterpret_cast<const platform::CUDADeviceContext&>(ctx).stream();
@@ -215,11 +212,8 @@ void gpu_scatter_input_grad_kernel(Tensor self, int dim, const Tensor& index,
     outer_dim_size *= index_dims[i];
   }
 
-  int64_t slice_size = 1;
-  for (int i = 1; i < grad_dims.size(); ++i) slice_size *= grad_dims[i];
-
   int block = 512;
-  int64_t n = slice_size * index_size;
+  int64_t n = inner_dim_size * select_dim_size * outer_dim_size;
   int64_t grid = (n + block - 1) / block;
   auto stream =
       reinterpret_cast<const platform::CUDADeviceContext&>(ctx).stream();