Add correct Input() shim to caffe2 operator impl (#16048)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/16048
This enables full shimming of the operator (previously it was only
Output() shimmed).
Reviewed By: smessmer
Differential Revision: D13468241
fbshipit-source-id: c853b775ab5cdcd968f4a6cc4766e91c3c6b1c45
