Follow up from https://crrev.com/c/1874378, declare these SSSE3
instructions using a separate macro that declares the right scope.

Bug: v8:9561
Change-Id: Ia4370a4dff9e9d13b08c5e95a45670556d6ff1e2
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1875657Reviewed-by: Deepti Gandluri <gdeepti@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64601}