This reverts commit 3a6f1135.

This reverts commit b532315d.

* mv floordiv to phi

* mv elementwise_pow to phi

* fix as review

* move reduce kernels into one file

* rename reduce_prod to prod

* move reduce sum/mean from math_kernel into reduce_kernel

* rm comment

* move elementwise_div grad

* change mutable_data to alloc

* fix compile bugs

* delete elementwise_sub kernel registry

* fix compile bugs in xpu ci

* fix bugs when run inference ci

* add layer norm

* add p norm

* add reduce sum

* refine layer norm register bf16 for cudnn811

* add bf16 cast for hip

* add unittest

* refine rocm

* refine layer_norm unittest

* refine reduce op

* refine unittest

* enhance atol for reduce unittest

* add ele_add

* add ele_mul

* add ele_sub

* sovle conflict

* fix npu

* refine ele_add

* add ele_mul unittest

* refine ele_sub

* refine ci

* refine unittest

* unify register macro

* rename declare macro

* fix infrt error

* rm reduce_sum raw kernel

* remove reduce_mean kernel

* remove reduce_mean kernel

* reduce support int and int64_t

* mean support int and int64_t type

* rename pten dir to phi

* rename namespace to phi

* rename infrt pten dir to phi

* resolve conflict

* rename pten to phi in cmake

* revert all infrt change

* change needed files

* fix infrt failed

* fix inference failed

* add more op int16 support

* fix xpu ci

* clean useless header in pten core

* fix compiled failed

* fix cmake target

* fix typo

* resolve conflict

* add kernel for c++ api

* fix compile bugs

* fix kunlun compile bugs

* perfect cmake

* fix compile bugs when run ci-inference

* fix compile bugs

* add non-raw kernel for fluid op

* fix compile bugs

* fix compile bugs

* fix unit test bug