The {TurboAssembler} already has logic to use the {lzcnt} and {tzcnt}
instructions if available, and otherwise falls back to a slightly
optimized variant of the previous code. Thus, we just call these
methods.

Drive-by: Use {movl} instead of {Set} for constant values, for
          consistency, readability and performance.

R=jkummerow@chromium.org

Bug: v8:9919
Change-Id: I6028fa63c0adc70e8b4a3e61b8377a1eacce5040
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1891350Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64674}