media: dt-bindings: ov2659: add powerdown/reset-gpios optional property

Add powerdown-gpios and reset-gpios to the list of optional properties
for the OV2659 camera sensor.

Signed-off-by: Benoit Parrot <bparrot@ti.com>
Acked-by: Lad, Prabhakar <prabhakar.csengg@gmail.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+samsung@kernel.org>