[media] coda: split userspace interface into encoder and decoder device

Userspace has a hard time making sense of format enumerations on V4L2
mem2mem devices if there are restrictions on which input and output
formats can be used together. Alleviate the problem by splitting the
video4linux device into separate encoder and decoder devices which list
only raw formats on one side and only encoded formats on the other side.
With this patch, the instance type (encoder or decoder) is already
determined by the open file operation.

Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Kamil Debski <k.debski@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>