media: dt-bindings: media: i2c: Add OV8865 bindings documentation

This introduces YAML bindings documentation for the OV8865
image sensor.

Co-developed-by: Kévin L'hôpital <kevin.lhopital@bootlin.com>
Signed-off-by: Kévin L'hôpital <kevin.lhopital@bootlin.com>
Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.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>