media: i2c: imx290: Add support for the mono sensor variant

Should be upstream commit 9bf52c7136d1

The IMX290 module is available as either mono or colour (Bayer).

Update the driver so that it can advertise the correct mono
formats instead of the colour ones.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Tested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>