Add OWNERS for power/ml

Change-Id: I163da12c827cb4880b561bf4099abdd758d17031
Reviewed-on: https://chromium-review.googlesource.com/1141456Reviewed-by: Dan Erat <derat@chromium.org>
Reviewed-by: Jia Meng <jiameng@chromium.org>
Commit-Queue: Jia Meng <jiameng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#575953}

chrome/browser/chromeos/power/ml/OWNERS

+amoylan@chromium.org
+derat@chromium.org
+jiameng@chromium.org
+martis@chromium.org