media: i2c: imx219: Don't store the current mode in the imx219 structure

The mode field of the imx219 structure is only used in
imx219_init_controls(), after the probe function sets it to point to the
default mode. Use the default mode directly when initializing controls,
and drop the mode field from the imx219 structure.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>