media: rcar-vin: move functions regarding scaling

In preparation of refactoring the scaling code move the code regarding
scaling to to the top of the file to avoid the need to add forward
declarations. No code is changed in this commit only whole functions
moved inside the same file.
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>