[llvm] [PowerPC][AIX] Refactor existing logic to handle non-zero offsets for aix-small-local-dynamic-tls (PR #89182)

[Felix via llvm-commits]

orcguru wrote:

> The change and the removal of the section makes sense since we need to account for local-dynamic now, so LGTM.

Thank you Amy! I will wait for a few more days before merge.

https://github.com/llvm/llvm-project/pull/89182