media: i2c: imx219: Correct the minimum vblanking value

The datasheet for this sensor documents the minimum vblanking as being
32 lines. It does fix some problems with occasional black lines at the
bottom of images (tested on Raspberry Pi).

Signed-off-by: David Plowman <david.plowman@raspberrypi.com>
Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Signed-off-by: Jai Luthra <jai.luthra@ideasonboard.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>