media: dt-bindings: media: ovti,ov9282: Add optional regulators

The OV9282 image sensor takes 3 voltage supplies, so
define the relevant regulators.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Acked-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>