[llvm] [AMDGPU] Strengthen preload intrinsics to noundef and nonnull (PR #92801)

[Krzysztof Drewniak via llvm-commits]

krzysz00 wrote:

Ok, so, implicit argument pointer can reasonably be null, and I'd think library code could reasonably check for implicit arguments being/not being there to avoid crashes or something like that.

I'm tempted to mumble the phrase "calling for the kernel argument pointer in non-kernel functions is undefined (and a bad idea anyway, you don't know what you'll find there)" at the kernarg pointer though

https://github.com/llvm/llvm-project/pull/92801