clang/AMDGPU: Require 16-bit-insts for half typed image builtins (#205368)
Typed image load/store operations with 16-bit elements require d16
support which was introduced in gfx8. They were previously gated only
on image-insts, so they were wrongly accepted on targets that have
images but lack 16-bit support (e.g. gfx700), where the backend then
fails to select.
Co-Authored-By: Claude (Opus 4.8) <noreply@anthropic.com>