[clang] [llvm] [PowerPC] Add initial support for AMO load builtins (PR #167790)

[Maryam Moghadas via cfe-commits]

maryammo wrote:

Since the amo1 branch was in my own fork, and I needed to move it to the upstream repository to be able to properly create a stacked PR, I will close this one. The new PR will be https://github.com/llvm/llvm-project/pull/168746.

https://github.com/llvm/llvm-project/pull/167790