device: Add armansito@ to OWNERS.

armansito@ is already an owner of device/bluetooth and device/nfc, so
make him and OWNER for the occasional unit test additions to device_tests.gyp.

BUG=none
R=rpaquay@chromium.org

Review URL: https://codereview.chromium.org/886443003

Cr-Commit-Position: refs/heads/master@{#313823}

device/OWNERS

+armansito@chromium.org
 keybuk@chromium.org
 reillyg@chromium.org
 rockot@chromium.org