media: i2c: imx296: Use v4l2_subdev_get_fmt()

The imx296 driver uses the subdev active state, there's no need to
implement the .get_fmt() operation manually. Use the
v4l2_subdev_get_fmt() helper instead.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>