[torch.fx] Pass placeholders through delegate too (#43432)
Summary:
It's useful if we add additional attributed to nodes in the graph - it's easier to set the attribute on all nodes, even if the value would happen to be None.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/43432
Reviewed By: jamesr66a
Differential Revision: D23276433
Pulled By: dzhulgakov
fbshipit-source-id: c69e7cb723bbbb4dba3b508a3d6c0e456fe610df
