fp16 python still needed

fp16 python interface is used here
https://github.com/Maratyszcza/NNPACK/blob/master/src/x86_64-fma/blas/shdotxf.py#L4

but has been removed here
https://github.com/Maratyszcza/FP16/commit/07ff4fd681127d86a06cb8d369cb96988de402e6

This breaks the building of nnpack.