Fix 'initialized after field' error (pytorch#30908)

Summary:
Pull Request resolved: pytorch#30908

Same as title.

Test Plan: Wait for CI to clear.

Reviewed By: bddppq, xw285cornell

Differential Revision: D18862837

fbshipit-source-id: bc34356b85774fc20ba46d321c8a2bb5d5c727f6

Author: Serhat Yilmaz

aten/src/ATen/native/cuda/Reduce.cuh

@@ -300,14 +300,14 @@ struct ReduceOp {
   ReduceOp(ops_t ops, ReduceConfig config, InputCalculator input_calc, OutputCalculator output_calc,
            const void* src, char* dst0, optional<char*> dst1, void* acc_buf, void* cta_buf, int* semaphores, arg_t ident, int noutputs)
     : ops(ops)
+    , ident(ident)
     , config(config)
     , input_calc(input_calc)
     , output_calc(output_calc)
     , src(src)
     , acc_buf(acc_buf)
     , cta_buf(cta_buf)
     , semaphores(semaphores)
-    , ident(ident)
     , noutputs(noutputs) {
     dst[0] = dst0;
     if (dst1.has_value()) {