[llvm] [AMDGPU] Support alloca in AS0 (PR #136584)

[Shilei Tian via llvm-commits]

shiltian wrote:

> > You mean in the `AAAddressSpace`?
> 
> No. I mean in the detection of the queue pointer uses and flat scratch init. The places looking for ADDR_SPACE_CAST_PRIVATE_TO_FLAT

Done.

https://github.com/llvm/llvm-project/pull/136584