Move mode_t declaration in PadOptions (#28760)
Summary:
Based on the discussion in https://github.com/pytorch/pytorch/pull/28413#discussion_r338839489, putting anything that's not tagged as `public:` under a `TORCH_ARG` line would hide it under `private:`. To get around this problem, we should move the `mode_t` declaration at the top of the PadOptions declaration.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/28760
Differential Revision: D18165117
Pulled By: yf225
fbshipit-source-id: cf39c0a893822264cd6a64cd887729afcd84dbd0
