Enable fp16 for CUDA SparseLengthsSum/Mean (#44089)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/44089
Add support of fp16 as input type in SparseLengthSum/Mean caffe2 operator
Reviewed By: xianjiec
Differential Revision: D23436877
fbshipit-source-id: 02fbef2fde17d4b0abea9ca5d17a36aa989f98a0
