media: imx: imx-mipi-csis: Add version register

Register at offset 0x00 isn't documented, but the NXP BSP
imx8-mipi-csi2-sam driver defines it as a version register. Tests on
i.MX7D and i.MX8MP have confirmed this, with values matching the version
of the IP core specified in the respective reference manuals.

This commit doesn't make use of the version register at runtime as the
compatible strings are enough to identify the IP core version.
Nonetheless, capturing the information in register definitions that
don't affect the code negatively is useful for future development.

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