[clang] clang/AMDGPU: Require 16-bit-insts for half typed buffer format builtins (PR #205367)

[Shilei Tian via cfe-commits]

https://github.com/shiltian requested changes to this pull request.

We definitely don't need to do the feature check manually.

https://github.com/llvm/llvm-project/pull/205367