[llvm] AMDGPU/GlobalISel: Add test showing s_andn2_b32/b64 is not formed from booleans (PR #115537)

[Jay Foad via llvm-commits]

jayfoad wrote:

I can see that s_andn2 is not formed in these tests, but I can't see how it would be any better if it was formed. What's the point of this?

https://github.com/llvm/llvm-project/pull/115537