Drive-by: also cleanup ppc 32-bit support

R=joransiu@ca.ibm.com

Change-Id: I0596405ae59a0f18db7eb0f480944b8530a31113
Reviewed-on: https://chromium-review.googlesource.com/c/1262936Reviewed-by: Joran Siu <joransiu@ca.ibm.com>
Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Junliang Yan <jyan@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#56419}