media: i2c: ov13858: Replace client->dev usage

media: i2c: ov13858: Replace client->dev usage

The driver needs to access the struct device in many places, and
retrieves it from the i2c_client itself retrieved with
v4l2_get_subdevdata(). Store it as a pointer in struct ov13858 and
access it from there instead, to simplify the driver.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Reviewed-by: Mehdi Djait <mehdi.djait@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>