A Load(kWord32) generates a movl instruction, which clears the high word
of a register already.

R=bmeurer@chromium.org

Change-Id: I835e5549483043a3faea08a1223070514f634c9e
Reviewed-on: https://chromium-review.googlesource.com/729863Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48777}