[llvm] [AMDGPU] Add missing GFX10 buffer format d16 hi instructions (PR #84809)

[Jay Foad via llvm-commits]

jayfoad wrote:

> > Can you please add a codegen test to make sure they work?
> 
> I am not expecting codegen to use these instructions (without some extra work) but I can check.

These instructions have existed since GFX9. As far as I can tell we have never implemented codegen for them.

https://github.com/llvm/llvm-project/pull/84809