With statically in-bounds memory accesses (implemented in
https://crrev.com/c/2919827) we would only have an offset but no index
register for {TraceMemoryOperation}. This CL fixes that situation.

R=thibaudm@chromium.org

Bug: chromium:1248024
Change-Id: I856b263a560cb71791c61e446e78dd99c9664190
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3149464Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/main@{#76763}