[llvm] [AMDGPU][AsmParser][NFC] Give isImmLiteral() a better name. (PR #153395)

[Jay Foad via llvm-commits]

jayfoad wrote:

Is ImmTyNone used both for values that can be encoded as inlines (like 3) and those that need to be literals (like 999)?

So you want a name that means something like "an immediate that is rendered as a plain old number in assembler source"?

https://github.com/llvm/llvm-project/pull/153395