ozone: add NV12 to GetBufferFormatFromFourCCFormat

crrev.com/2533163002 changed the internal format representation
of the GbmBuffer class. The function used to convert back to the
gfx::BufferFormat type, GetBufferFormatFromFourCCFormat, is missing
NV12. This format gets passed from the ARC++ container to Chrome, so
video playback isn't working on some platforms. Let's fix this by
adding the format.

BUG=b:33011213
TEST=Play Youtube App video on minnie

R=dnicoara@chromium.org, dcastagna@chromium.org, tfiga@chromium.org,
posciak@chromium.org

Review-Url: https://codereview.chromium.org/2562903002
Cr-Commit-Position: refs/heads/master@{#437608}

ui/ozone/platform/drm/common/drm_util.cc

@@ -375,6 +375,8 @@ gfx::BufferFormat GetBufferFormatFromFourCCFormat(int format) {
       return gfx::BufferFormat::BGR_565;
     case DRM_FORMAT_UYVY:
       return gfx::BufferFormat::UYVY_422;
+    case DRM_FORMAT_NV12:
+      return gfx::BufferFormat::YUV_420_BIPLANAR;
     case DRM_FORMAT_YV12:
       return gfx::BufferFormat::YVU_420;
     default: