media: rcar-vin: align pixelformat check

If the pixelformat is not supported it should not fail but be set to
something that works. While we are at it move the two different
checks of the pixelformat to the same statement.

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>