media: i2c: ov5645: Use local `dev` pointer for subdev device assignment

While assigning the subdev device pointer, use the local `dev` pointer
which is already extracted from the `i2c_client` pointer.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Tommaso Merciai <tomm.merciai@gmail.com>
Tested-by: Tommaso Merciai <tomm.merciai@gmail.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>