This reverts commit 94f2212b.

Reason for revert: Failures https://ci.chromium.org/p/v8/builders/ci/V8%20Win32%20-%20debug/29008?

Original change's description:
> [wasm-simd] Scalar lowering for extended multiply
>
> R=​bbudge@chromium.org
>
> Bug: v8:11262
> Change-Id: Idd6a7514a16c561832af603dbf63779a0e402f45
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2603771
> Reviewed-by: Bill Budge <bbudge@chromium.org>
> Commit-Queue: Zhi An Ng <zhin@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#71920}

TBR=bbudge@chromium.org,zhin@chromium.org

Change-Id: Ic32ac37ee630c644c1f0605cfa3ca7842c52ce15
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:11262
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2612544Reviewed-by: Zhi An Ng <zhin@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71922}