[clang] [llvm] [AMDGPU] Apply alignment attr for make.buffer.rsrc (PR #166914)

[Shilei Tian via llvm-commits]

shiltian wrote:

> So I think that adding generic handling for "this returns an existing pointer without capturing" might be the right call

In the previous PR that handles the `ptrmask`, in an offline discussion with @Shoreshen at one point, I recommended to introduce a call back (not using the simplified value call back) to tell `AAAlign` that, the alignment of this value is same as something else. With this call back, I'd imagine we don't need special handling in the generic code, because we just need to say, if the value is `llvm.amdgpu.make.buffer.rsrc`, its alignment is same as its pointer operand, and then the generic AA would just query the pointer operand.

https://github.com/llvm/llvm-project/pull/166914