[clang] [llvm] [PowerPC][ISelLowering] Support -mstack-protector-guard=tls (PR #110928)

[Alexander Richardson via cfe-commits]

https://github.com/arichardson approved this pull request.

This LGTM but would be good to have someone who actually knows PPC to also review it.

https://github.com/llvm/llvm-project/pull/110928