Added owners for enterprise code.

BUG=none

Review-Url: https://codereview.chromium.org/2836423003
Cr-Commit-Position: refs/heads/master@{#467309}

chrome/browser/extensions/api/enterprise_platform_keys/OWNERS

 emaxx@chromium.org
+drcrash@chromium.org

chrome/browser/extensions/api/enterprise_platform_keys_private/OWNERS

-dkrahn@chromium.org
-mnissler@chromium.org
+emaxx@chromium.org
+drcrash@chromium.org
 bartfab@chromium.org
+mnissler@chromium.org
+dkrahn@chromium.org