It was used only with Register inputs, so we can replace its uses with
the Registers themselves.

Change-Id: I1ea3ed88ee41177b696a7281cdf3b90fefdc5870
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1886916Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64639}