media: rcar-vin: set a default field to fallback on

If the field is not supported by the driver it should not try to keep
the current field. Instead it should set it to a default fallback. Since
trying a format should always result in the same state regardless of the
current state of the device.

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>