[llvm] AMDGPU: Assume true in getVOPNIsSingle helpers (PR #98516)

[Joe Nash via llvm-commits]

Sisyph wrote:

> The situation is a mess. We have isCodeGenOnly and isAsmParserOnly, so you can construct printable but not disassembled pseudo instructions. I can't test this directly but it will break all the codegen and disassembler tests in a future commit

Based on that it sounds like things will eventually reach a reasonable state. And this patch is NFC in tree, so it does not hurt. Ok with me.

https://github.com/llvm/llvm-project/pull/98516