media: dt-bindings: media: i2c: max9286: Add property to select bus width

The GMSL serial data bus width is normally selected by the BWS pin, but
it can also be configured by software. Add a DT property that allows
overriding the value of the BWS-selected bus width to support systems
whose BWS pin doesn't result in the correct value.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>