This is a partial revert of https://crrev.com/c/2457669/.

This change is slightly longer (in code-generator-x64.cc) because we
also implement support when SSE4_2 is not supported (the reverted change
seems to assume SSE4_2, which is not always the case). This code
sequence is from https://github.com/WebAssembly/simd/pull/412.

Bug: v8:11415
Change-Id: I3eef415667b4142887cf1c449d27d19ba5bbd208
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2683219
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Reviewed-by: Bill Budge <bbudge@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72611}