Jaideep has been regularly contributing PPC and S390 changes recently.
Adding him as owner/reviewer to PPC / S390 specific directories.

R=joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com, mbrandy@us.ibm.com
BUG=

Review-Url: https://codereview.chromium.org/2024533003
Cr-Commit-Position: refs/heads/master@{#36589}