Add support for the UDS (Up Down Scaler) found in some Gen3 SoCs.

Not all Gen3 SoCs have scalers, and for those that do it's only
available to the master node of each VIN group. The setup for which SoCs
and nodes have access to a scaler are dealt with at probe time and then
function transparently reusing the schema from the already present Gen2
scaler.
Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>