[llvm] [X86][Combine] Ensure single use chain in extract-load combine (PR #136520)

[Evgenii Kudriashov via llvm-commits]

e-kud wrote:

There are two commits in the PR. If the test looks ok, I'll precommit it so PR itself has only a change of restored spills.

https://github.com/llvm/llvm-project/pull/136520