[llvm] [AMDGPU] Add lit() asm operand modifier for SP3 compatibility. (PR #68839)

[Jay Foad via llvm-commits]

jayfoad wrote:

> abs(neg()) is not. Which also makes sense, as you cannot really do abs(neg()) in a non-constant case

abs(neg(x)) could be treated as abs(x).

https://github.com/llvm/llvm-project/pull/68839