[clang] [llvm] [PowerPC] Add support for -mcpu=pwr11 / -mtune=pwr11 (PR #99511)

[Chen Zheng via cfe-commits]

https://github.com/chenzheng1030 commented:

Basically you need to handle P11 for all the places where P10 is handled, seems you are missing below places:
1: we need handling in `LoadOpcodesForSpill` and `StoreOpcodesForSpill` for P11. Even for now P11 may already use the model of P10, we need at least some comments there to say P11 is reusing the same model with P10.
2: in `PPCISelLowering.cpp`, we also need to handle P11 for function `combineMUL` and `getPrefLoopAlignment`.
3: in `Host.cpp`, the funciton `getHostCPUName()`

https://github.com/llvm/llvm-project/pull/99511