[media] coda: implement VBV delay and buffer size controls

The encoder allows to specify the VBV model reference decoder's initial
delay and buffer size. Export the corresponding V4L2 controls.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>