CHROMIUM: [media] rk3288-vpu: Add VP8 decoder to V4L2 API implementation

CHROMIUM: [media] rk3288-vpu: Add VP8 decoder to V4L2 API implementation

This patch extends existing implementation of required V4L2 API calls
with code required for VP8 decoder.

BUG=chrome-os-partner:33728
TEST=video_encode_accelerator_unittest;video_decode_accelerator_unittest

Signed-off-by: ZhiChao Yu <zhichao.yu@rock-chips.com>
Signed-off-by: Tomasz Figa <tfiga@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/239814
Reviewed-by: Pawel Osciak <posciak@chromium.org>
Change-Id: I633687b7223c25f46d2373b964ceb1fe29f02b2f
Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
Signed-off-by: Yakir Yang <ykk@rock-chips.com>