media: dt-bindings: media: document imx8mq support for imx7-csi

Add the fsl,imx8mq-csi compatible string to the bindings for nxp,imx7-csi.
The i.MX8MQ SoC contains the same CSI bridge controller as the i.MX7.

Signed-off-by: Martin Kepplinger <martin.kepplinger@puri.sm>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>