Enable conv+add fusion, same as conv+sum (#15268)
Summary:
Enable conv+add fusion, same as conv+sum
Caution: only element-wise add is supported on IDEEP without scalar
broadcast. Otherwise, the fusion is illegal.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/15268
Differential Revision: D13577375
Pulled By: yinghai
fbshipit-source-id: 92c9c4b667c5ca5f7a262a5bffaa8aa68eeff3bd
