media: rcar-vin: enable Gen3 hardware configuration

Add the register needed to work with Gen3 hardware. This patch adds
the logic for how to work with the Gen3 hardware. More work is required
to enable the subdevice structure needed to configure capturing.

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>