Documentation: media: camera-sensor: Use link to upstream DT bindings

The Documentation/devicetree/bindings/clock/clock-bindings.txt file is
deprecated and points to clock-bindings.yaml, which is not hosted in the
kernel source tree. Use an HTTPS link to refer to the YAML binding
document.

While at it, drop "currently" from the paragraph, as the whole file
refers to the current recommended practices except where explicitly
noted.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>