media: coda: lock capture queue wakeup against encoder stop command

Make sure that an encoder stop command running concurrently with an
encoder finish_run always either flags the last returned buffer or wakes
up the capture queue to signal the end of stream condition afterwards.

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>