reinterpret_cast to std::atomic was missing const.

Bug: chromium:1108537
Change-Id: Ib737418bddbef6774deafa9714b0efcf2e3fd07c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2332797
Auto-Submit: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69194}