[llvm] [AMDGPU] Update hasUnwantedEffectsWhenEXECEmpty (PR #97982)

[Jay Foad via llvm-commits]

https://github.com/jayfoad commented:

Seems reasonable, but I don't really feel super confident about whether this could break anything or fix anything. Does it have any effect on Vulkan CTS?

https://github.com/llvm/llvm-project/pull/97982