media: ov2680: Add link-freq and pixel-rate controls

Add read-only link-freq and pixel-rate controls. This is necessary for
the sensor to work with the ipu3-cio2 driver and for libcamera.

Acked-by: Rui Miguel Silva <rmfrfs@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>