[media] coda: add bitstream ringbuffer handling for decoder

Add a bitstream ringbuffer using kfifo. Queued source buffers are to be copied
into the bitstream ringbuffer immediately and marked as done, if possible.

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>