The hight 32 bits of the result of mulhw are undefined and need
to be cleared manually.

Change-Id: I0e746898aa26a7970ab59b89c374afd1377028ea
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2347208Reviewed-by: Junliang Yan <jyan@ca.ibm.com>
Commit-Queue: Milad Farazmand <miladfar@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#69318}