media: rockchip: rga: use macros for testing buffer type

Use the provided V4L2_TYPE_IS_{OUTPUT,CAPTURE} macros to check if the
buffer or queue is OUTPUT or CAPTURE. The macros work also work for the
_MPLANE buffer and queue types and make it easier to switch to the
multi-planar API.

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