[Static Runtime] Out version for softmax (#64243)

[Static Runtime] Out version for softmax (#64243)

Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/64243

Test Plan:
```
> buck run //caffe2/benchmarks/static_runtime:static_runtime_cpptest -- --v=1
...
V0830 16:35:22.524479 613839 impl.cpp:1410] Switch to out variant for node: %5 : Tensor = aten::softmax(%a.1, %dim.1, %dtype.1)
...
[       OK ] StaticRuntime.IndividualOps_Softmax (803 ms)
```

Reviewed By: hlu1

Differential Revision: D30656149

fbshipit-source-id: 115b7b4a75448fd6a5c526808080ca9a4251302c