media/gpu/v4l2: use OnceClosure for V4L2DecodeSurface

V4L2DecodeSurface's callback has been changed to a OnceClosure, and thus
does not need a specialized type to describe it, so remove it.

BUG=941330
TEST=VDAtest passes on Minnie.

Change-Id: I5e6a12ecb48c3a339574056cbfc699f4e00b5dd1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1647304
Reviewed-by: Hirokazu Honda <hiroh@chromium.org>
Commit-Queue: Alexandre Courbot <acourbot@chromium.org>
Cr-Commit-Position: refs/heads/master@{#668288}
2 files changed