[clang] [HIP] Remove redundant device optimization pipeline (PR #206350)

[Yaxun Liu via cfe-commits]

yxsamliu wrote:

Closing this for now. #206961 reverted the default non-RDC `--no-lto` linker-wrapper path, so this PR no longer applies to the default HIP path.

The compile-time issue still matters. We need to find another way to parallelize the Clang device compilation before LTO, instead of relying on this non-LTO wrapper path.

https://github.com/llvm/llvm-project/pull/206350