[clang] [SystemZ][Clang]Use the function name from the source for name PPA1 (PR #209215)

[Oliver Hunt via cfe-commits]

ojhunt wrote:

> @ojhunt any update?

Sorry have been on vacation, and was trying really hard to not read my work mail so missed this. Looking now.

https://github.com/llvm/llvm-project/pull/209215