media: rcar-vin: extend {start, stop}_streaming to work with media controller

The procedure to start or stop streaming using the non-MC single
subdevice and the MC graph and multiple subdevices are quite different.
Create a new function to abstract which method is used based on which
mode the driver is running in and add logic to start the MC graph.

Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>