Add fx2trt support to resnet50 (#661)
Summary:
To test, run:
`python run.py resnet50 --fx2trt -d cuda`
after making sure you have installed TensorRT.
Latency after enabling fx2trt:
```
GPU Time: 5.864 milliseconds
CPU Dispatch Time: 0.438 milliseconds
CPU Total Wall Time: 5.869 milliseconds
```
Latency without fx2trt, run with `python run.py resnet50 -d cuda`:
```
GPU Time: 19.148 milliseconds
CPU Dispatch Time: 12.143 milliseconds
CPU Total Wall Time: 19.148 milliseconds
```
Pull Request resolved: https://github.com/pytorch/benchmark/pull/661
Reviewed By: 842974287
Differential Revision: D33200149
Pulled By: xuzhao9
fbshipit-source-id: f7ccdf918991f0fc2535fcce879043f46da618c9
