Add bindings for Renesas R-Car ISP Channel Selector IP. The ISP is
responsible for filtering the MIPI CSI-2 bus and directing the different
CSI-2 virtual channels to different R-Car VIN instances (DMA engines)
for capture.

Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>