[fx2trt] break down div (#71172)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/71172
Break down div to smaller ops to make those div ops look like all other elementwise ops.
Use operator div ops instead of torch div if possible to avoid converting literal numbers to torch tensor (like in the following).
```
a = 1
b = 2
// `c` would be 0.5
c = a / b
// `c` would be torch.tensor([0.5])
c = torch.div(a, b)
```
The problem we saw on shufflenet is that there's size op followed by a div op which results in int64 tensors in acc traced graph (acc tracer turns operator.div to acc_ops.div which uses torch.div). And trt splitter splits out the reshape op that consumes the div op because we have a rule to split out ops that takes in int64 tensors as inputs.
Test Plan: Unit tests.
Reviewed By: wushirong
Differential Revision: D33482231
fbshipit-source-id: 508a171520c4e5b4188cfc5c30c1370ba9db1c55
