media: dt-bindings: Add OmniVision OV08X40

Add bindings for the already upstream OV08X40 to enable usage of this
sensor on DTS based systems.

Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
[Sakari Ailus: Add the file to MAINTAINERS.]
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>