[HIP] Fix regression about `__fp16` args and return value

HIP allows __fp16 as function arguments and return value by passing
-fallow-half-arguments-and-returns to clang through hipcc.

https://reviews.llvm.org/D133885 removed -fallow-half-arguments-and-returns
and add a TargetInfo member to control it.

This caused regressions in some HIP apps
(https://github.com/ROCm-Developer-Tools/HIP/issues/3178).

Reviewed by: Artem Belevich

Differential Revision: https://reviews.llvm.org/D145345

Fixes: https://github.com/ROCm-Developer-Tools/HIP/issues/3178