media: dt-bindings: media: imx274: Convert to json-schema

Convert the imx274 bindings document to json-schema and update
the MAINTAINERS file accordingly.

Reviewed-by: Luca Ceresoli <luca@lucaceresoli.net>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>