[clang] [AMDGPU] Add sema check for global_atomic_fadd_v2f16 builtin (PR #158145)

[Shilei Tian via cfe-commits]

shiltian wrote:

I'm not sure what this PR is trying to fix, but we do have type enforcement in `clang/include/clang/Basic/BuiltinsAMDGPU.def`?

https://github.com/llvm/llvm-project/pull/158145