media: i2c: imx290: Implement HBLANK and VBLANK controls

Add support for the V4L2_CID_HBLANK and V4L2_CID_VBLANK controls to the
imx290 driver. Make the controls read-only to start with, to report the
values to userspace for timing calculation.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>