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

[Jay Foad via llvm-commits]

jayfoad wrote:

> Why were these initially disabled?

I don't know. I wasn't involved. @rampitec do you remember?

> 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.

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