This removes dead code handling register arguments to runtime calls,
which do not exist currently.

R=mstarzinger@chromium.org

Change-Id: Ia5fdd60d0036f87a335bbe42b5790d1b86aa0add
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1715448Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62889}