Define a new vendor property in the maxim,max9286 binding schema.

The new property allows to declare that the remote camera
power-over-coax is controlled by one of the MAX9286 gpio lines.

As it is currently not possible to establish a regulator as consumer
of the MAX9286 gpio controller for this purpose, the property allows to
declare that the camera power is controlled by the MAX9286 directly.

The property accepts a gpio-index (0 or 1) and one line polarity
flag as defined by dt-bindings/gpio/gpio.h.
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>