media: i2c: imx290: Use V4L2 subdev active state

Upstream commit a2514b9a

Use the V4L2 subdev active state API to store the active format. This
simplifies the driver not only by dropping the imx290 current_format
field, but it also allows dropping the imx290 lock, replaced with the
state lock.

The lock check in imx290_ctrl_update() can be dropped as
imx290_set_fmt() can't be called anywmore with which set to ACTIVE
before controls are initialized.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>