Move FakeFP16 back to internal to remove dependency on MKL (#36297)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/36297
Pull Request resolved: https://github.com/pytorch/FBGEMM/pull/343
We moved FakeFP16 back to close source and kept `RoundToFloat16` function in "fbgemm/FbgemmConvert.h".
This is because FakeFP16 introduced dependency on MKL in the FBGEMM core. Also it doesn't seem to be needed for open source, as it is not used anywhere.
Test Plan: CI
Reviewed By: jspark1105
Differential Revision: D20937962
fbshipit-source-id: 9487a9fd2282b6df2f754c22bea36f2255a5c791
