media: imx.rst: Provide the OV560 module part number

In order to improve the documentation, provide the OV5640 MIPI module
part number that is used on the imx6q-sabresd board.

Signed-off-by: Fabio Estevam <festevam@gmail.com>
Reviewed-by: Steve Longerbeam <slongerbeam@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>