By accident a "w"-register was used to push references on the stack
instead of an "x"-register. This CL fixes the bug.

CC=jkummerow@chromium.org
R=thibaudm@chromium.org

Bug: v8:11596
Change-Id: I5e0b6bebdc763f8d30fd2891786f6c82b9c1e7ac
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2783038Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#73633}