[llvm] [AMDGPU] Don't assume a hazard for empty inline asm (PR #223526)

[Ralf Jung via llvm-commits]

RalfJung wrote:

Out-of-tree backends can of course choose to violate the spec given in the LangRef, but upstream should discourage such behavior because it reduces the value of LLVM IR ad a shared IR with shared semantics.

https://github.com/llvm/llvm-project/pull/223526