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

[Shilei Tian via cfe-commits]

shiltian wrote:

The builtin infrastructure can perform this check automatically, and that's how all the other builtins handle it today. If you don't think this is the right place for the check, I'd rather move the generic feature check somewhere else.

Also, this check doesn't work, as shown by ROCM-26503. You need more than this to handle the case correctly.

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