Migrate kl_div_backward from CUDA_tensor_apply3 to TensorIterator (#34022)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/34022
Test Plan: Imported from OSS
Differential Revision: D20196080
Pulled By: VitalyFedyunin
fbshipit-source-id: 265884dc01c3260197776ee5baaadbe6b523fede
