v4l2_stateful_decoder: Add HEVC mini parser

This adds an HEVC bitstream parser for use with v4l2_stateful_decoder.
The parser is used to split an HEVC Annex-B bitstream into frames. If
there are metadata NALU's before the next frame is completed, they will
be included in the next frame's buffer. If the next frame is made up of
multiple slices, all slices will be included with the next frame's
buffer.

BUG=b:227248846
TEST=Manually tested with HEVC sources on Trogdor

Change-Id: Ib51d23f75f6ce67bafc54c401116a927d41b521c
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/drm-tests/+/3567602
Tested-by: Nathan Hebert <nhebert@chromium.org>
Reviewed-by: Fritz Koenig <frkoenig@chromium.org>
Commit-Queue: Nathan Hebert <nhebert@chromium.org>
6 files changed