Revert of Clean up V4L2 codec-related flags and defines

Revert of Clean up V4L2 codec-related flags and defines (patchset #3 id:40001 of https://codereview.chromium.org/828063009/)

Reason for revert:
x86 Chrome compile failure due to https://code.google.com/p/chromium/issues/detail?id=455545.

Original issue's description:
> Clean up V4L2 codec-related flags and defines
>
> All arm platforms support V4L2 SVDA by default and use_v4l2_codec also governs V4L2 VDA/VEA now.
> Generates libv4l2 stub in GN file.
>
> BUG=449883
> TEST=build chrome and vda unittest on peach_pit, veyron_pinky, squawks,
> and panther_freon
>
> Committed: https://crrev.com/d5eeecc577f274bb8ed9d1954f263d83b5f00050
> Cr-Commit-Position: refs/heads/master@{#314536}

TBR=piman@chromium.org,wuchengli@chromium.org,henryhsu@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=449883
Committed: https://crrev.com/a3566c5c4784c9387ed188e1456dd557d9c7fca9
Cr-Commit-Position: refs/heads/master@{#314760}

[Pawel Osciak, 2015-02-05 05:06:13]

Created Revert of Clean up V4L2 codec-related flags and defines

[commit-bot: I haz the power, 2015-02-05 05:06:58]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/902773003/1

[commit-bot: I haz the power, 2015-02-05 05:07:44]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-05 05:08:42]

Patchset 1 (id:??) landed as
https://crrev.com/a3566c5c4784c9387ed188e1456dd557d9c7fca9
Cr-Commit-Position: refs/heads/master@{#314760}