Revert "Do not use unnecessary `membarrier()` on x86." am: 6c2275d43d am: 9fb3470099

Original change: https://android-review.googlesource.com/c/platform/art/+/2394352

Change-Id: I9976181f83830c00a50895fe61a59df9662207c0
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>