[llvm] [NFC][PowerPC] Use tablegen's MatchRegisterName() (PR #111553)

[Tom Stellard via llvm-commits]

tstellar wrote:

I didn't see your response in time and just filed an issue for this here: https://github.com/llvm/llvm-project/issues/126786

Maybe we can discuss it there.

https://github.com/llvm/llvm-project/pull/111553