media: i2c: imx219: Name all subdev state variables 'state'

Subdev state variables are named with a mix of 'state' and 'sd_state'
through the driver. To improve consistency, name them all 'state'.

Signed-off-by: Laurent Pinchart <laurent.pinchart@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>