Convert the simple OV5645 Device Tree binding to json-schema.

The previous binding marked the below properties as required which was a
driver requirement and not the device requirement so just drop them from
the required list during the conversion.
- clock-frequency
- enable-gpios
- reset-gpios

Also drop the "clock-names" property as we have a single clock source for
the sensor and the driver has been updated to drop the clk referencing by
name.
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.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@kernel.org>