[clang] [llvm] riscv: Support -mstack-protector-guard=tls (PR #108942)

[Keith Packard via cfe-commits]

keith-packard wrote:

I've retitled the commit messages to match llvm conventions and added a clean-up to replace another instance of `getParent()->getParent()` with `getModule()`.

https://github.com/llvm/llvm-project/pull/108942