[AOTInductor] Skip pre_grad_passes for exported graph. (#109246)
Summary:
We skip pre_grad_passes if graph comes from export (aten IR) since
pre_grad_passes (i.e. remove_identity) would not preserve meta["val"] in aten IR.
Differential Revision: D49246374
Pull Request resolved: https://github.com/pytorch/pytorch/pull/109246
Approved by: https://github.com/aakhundov
