media: dt-bindings: media: nxp,imx7-mipi-csi2: Indent example with 4 spaces

DT bindings examples are customarily indented with 4 spaces.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Rui Miguel Silva <rmfrfs@gmail.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>