[llvm] [AMDGPU][gfx1250] Also add a wait on xcnt before volatile accesses (PR #168852)

[Jay Foad via llvm-commits]

jayfoad wrote:

I think I get it - you don't want these accesses to be repeated just because some _other_ (prior) access failed address translation? Makes sense.

https://github.com/llvm/llvm-project/pull/168852