[Ozone-Drm] More LOG cleanup

[Ozone-Drm] More LOG cleanup

Make all the LOGs that follow DRM calls PLOGs since we're interested in
the error message.

Also add a few more LOGs during device probing just in case we end up in
odd states where the DRM device is controlled by another process and
we're trying to take ownership.

BUG=none

Committed: https://crrev.com/98598e7e4db7d709d0b50611e341c5c7f8227e43
Cr-Commit-Position: refs/heads/master@{#319716}

[dnicoara, 2015-03-09 17:39:57]

dnicoara@chromium.org changed reviewers:
+ spang@chromium.org

[dnicoara, 2015-03-09 17:39:58]

PTAL

[spang, 2015-03-09 17:45:16]

lgtm

[dnicoara, 2015-03-09 19:42:27]

The CQ bit was checked by dnicoara@chromium.org

[commit-bot: I haz the power, 2015-03-09 19:43:06]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/991963002/1

[commit-bot: I haz the power, 2015-03-09 20:07:11]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-03-09 20:08:04]

Patchset 1 (id:??) landed as
https://crrev.com/98598e7e4db7d709d0b50611e341c5c7f8227e43
Cr-Commit-Position: refs/heads/master@{#319716}