media: i2c: imx219: Implement get_selection

Implement the get_selection pad operation for the IMX219 sensor driver.
The supported targets report the sensor's native size, the crop default
rectangle and the crop rectangle.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>