Upstream S390 platform specific code to latest lkgr from the past 2 weeks.

R=danno@chromium.org,jkummerow@chromium.org,jochen@chromium.org,joransiu@ca.ibm.com,michael_dawson@ca.ibm.com,mbrandy@us.ibm.com
BUG=

Review URL: https://codereview.chromium.org/1799893002

Cr-Commit-Position: refs/heads/master@{#34787}