[llvm] [PowerPC] Remove carry register (PR #142420)

[Amy Kwan via llvm-commits]

amy-kwan wrote:

I see that @weiguozhi added the alias to XER to carry in https://github.com/llvm/llvm-project/commit/e6fb4e1f8ab3c76cbded23fbebdaec969205031f, presumably for inline asm.

However, the patch does not have a test case associated with it, so it would be good to check if we can come up with a test case and see if this change breaks it.

https://github.com/llvm/llvm-project/pull/142420