media: dt-bindings: add bindings for i.MX7 media driver

Add bindings documentation for i.MX7 media drivers.
The imx7 MIPI CSI2 and imx7 CMOS Sensor Interface.

Signed-off-by: Rui Miguel Silva <rui.silva@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>