media: dt-bindings: media: rockchip-vpu: Add RK3568 compatible

RK356x has Hantro G1 video decoder capable to decode MPEG2/H.264/VP8
video formats.

This patch adds RK3568 compatible in rockchip-vpu dt-bindings.

Tested on [1] with FFmpeg v4l2_request code taken from [2]
with MPEG2, H.642 and VP8 samples with results [3].

[1] https://github.com/warpme/minimyth2
[2] https://github.com/LibreELEC/LibreELEC.tv/blob/master/packages/multimedia/ffmpeg/patches/v4l2-request/ffmpeg-001-v4l2-request.patch
[3] https://github.com/warpme/minimyth2/blob/master/video-test-summary.txt



Signed-off-by: Piotr Oniszczuk <piotr.oniszczuk@gmail.com>
Reviewed-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>