* [Phi] Move Qr to the Phi

* [Phi] Regiter the cpu grad kernel for qr

* [Phi] Share the cuda kernels to lstsq

* [Phi] Remove some improper inlcude files

* [Phi] Modify codes based on the reviews

* [Phi] Remove unecessary files and add the cuda_only comment

* [Phi] Remove the unecessary include file

* [Phi] Remove qr_op.cu and lstsq_op.cu