media: ov2680: Store dev instead of i2c_client in ov2680_dev

Now that the cci_* register access helpers are used access to
the i2c_client after probe() is no longer necessary.

Directly store a struct device *dev pointing to &client->dev inside
ov2680_dev to make the code simpler.

Acked-by: Rui Miguel Silva <rmfrfs@gmail.com>
Reviewed-by: Daniel Scally <dan.scally@ideasonboard.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>