media: dt-bindings: media: allwinner,sun4i-a10-video-engine: Add R40 compatible

Allwinner R40 SoC contains video engine. Add compatible for it.

Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>