[lld] [lld][ELF][X86] Add missing X86_64_TPOFF64 case in switches (PR #77208)

[Nicholas Mosier via llvm-commits]

nmosier wrote:

Thanks for the comments. I updated the x86-64-tls-pie.s test as you suggested and removed the new one I previously had added. I also updated the commit message as suggested.

https://github.com/llvm/llvm-project/pull/77208