add `OpInfo` for `torch.nn.functional.mse_loss` (#62254)
Summary:
Addresses facebookresearch/functorch#78.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/62254
Reviewed By: malfet
Differential Revision: D30013331
Pulled By: zou3519
fbshipit-source-id: e3242cb97d1f061b932e3e0ed589f1ee6a291512
