[clang] [llvm] [PowerPC] Support local-dynamic TLS relocation on AIX (PR #66316)

[Felix via cfe-commits]

orcguru wrote:

> A question: For `PPCTLSDynamicCall.cpp`, would it be better if we instead reworded some of the sentences and not use `Load*@toc`?
> 
> I thought about this for a bit and I think the full sentences may be a bit better, so I added some sample comment suggestions, but if you think keeping the `Load*@toc` in the comments is better and more clear, then I think you can feel free to disregard the suggestion. However, if we are keeping the `Load*@toc`, it might be better to capitalize `TOC` instead.

Updated according to the suggestions. Thank you!

https://github.com/llvm/llvm-project/pull/66316