media: rcar-vin: all Gen2 boards can scale simplify logic

The logic to preserve the requested format width and height are too
complex and come from a premature optimization for Gen3. All Gen2 SoC
can scale and the Gen3 implementation will not use these functions at
all so simply preserve the width and height when interacting with the
subdevice much like the field is preserved simplifies the logic quite a
bit.

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>