mediatek: provide NV12 buffers for video decoding for MT8183

mediatek: provide NV12 buffers for video decoding for MT8183

crrev.com/c/1767450 changed the default android flexible buffer format
back to YV12, but the video decoding scenario on MT8183 requires NV12
buffers. Add an exception for this case.

BUG=b:141732718
TEST=Play H.264 video with acceleration using both Chrome and Android's
Youtube.

Change-Id: Ie4b80389b22650450ea45f5cdea36a00360899a9
Reviewed-on: https://chromium-review.googlesource.com/1833362
Tested-by: Alexandre Courbot <acourbot@chromium.org>
Commit-Ready: Alexandre Courbot <acourbot@chromium.org>
Legacy-Commit-Queue: Commit Bot <commit-bot@chromium.org>
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>