media: coda: mark last returned frame

If reordering is not enabled, the last decoded frame has to be the last
returned buffer. Otherwise wait for the firmware to report no more
frame to display. In that case the return buffer is the last one as
well, and can be reported as such.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>