This reverts commit 3600aabf.

Reason for revert: Causes test failures on AIX and PPC Linux.

Original change's description:
> ppc: [liftoff] implement AtomicExch and AtomicCmpExch
>
> Change-Id: Ida66b9c42cfb9bd5b59a83188a2dfa0d602d4036
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3192427
> Reviewed-by: Milad Fa <mfarazma@redhat.com>
> Commit-Queue: Junliang Yan <junyan@redhat.com>
> Cr-Commit-Position: refs/heads/main@{#77148}

Change-Id: If6ee4b050945b706c36a344abb844c7b73b2aba1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3198736Reviewed-by: Milad Fa <mfarazma@redhat.com>
Commit-Queue: Junliang Yan <junyan@redhat.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/heads/main@{#77199}