move code to Blas.cpp, clean up THC magma (#58526)
Summary:
To improve compilation times
Pull Request resolved: https://github.com/pytorch/pytorch/pull/58526
Reviewed By: malfet
Differential Revision: D28540035
Pulled By: ngimel
fbshipit-source-id: 01a6b1e2b12aa246c5ecfa810ad4e87bde040553
