media: dt-bindings: media: renesas,jpu: Convert to json-schema

Convert the Renesas JPEG Processing Unit Device Tree binding
documentation to json-schema.

Document missing properties.
Update the example to match reality.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Mikhail Ulyanov <mikhail.ulyanov@cogentembedded.com>
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>