[llvm] AMDGPU: Avoid crashing on statepoint-like pseudoinstructions (PR #170657)

[Robert Imschweiler via llvm-commits]

https://github.com/ro-i commented:

I currently don't really know anything specific about stackmap stuff.
Your ISel choices match those in `X86TargetLowering` tho, so seems kinda proven

https://github.com/llvm/llvm-project/pull/170657