media: i2c: adv7604: Enable video adjustment

The video adjustments (contrast, brightness, saturation and hue) are
ignored by default by the device when the VID_ADJ_EN bit is clear. The
corresponding V4L2 controls exposed by the drivers have thus no effect.
Fix this by setting the VID_ADJ_EN bit.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Tested-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>