media: rockchip: rga: add NV12M support

Add support for the multi-planar variants of NV12. The RGA is now able
to exchange DMABUFs with other devices that only support multi-planar
NV12, for example the Hantro JPEG encoder.

Signed-off-by: Michael Tretter <m.tretter@pengutronix.de>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>