We've already been zero-extending 32-bit offset registers since
https://chromium-review.googlesource.com/c/v8/v8/+/2917612,
but that patch only covered the case where offset_imm == 0.
When there is a non-zero offset, we need the same fix.

Bug: chromium:1224882,v8:11809
Change-Id: I1908f735929798f411346807fc4f3c79d8e04362
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2998582
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75500}