media: imx.rst: Provide an example for unprocessed video capture

The current example for imx6q-sabresd is for a direct conversion pipeline.

Provide an extra example using unprocessed video capture for completeness.

Signed-off-by: Fabio Estevam <festevam@gmail.com>
Reviewed-by: Steve Longerbeam <slongerbeam@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>