[media] coda: replace completion with mutex

Not only do we need to wait for job completion when we want to
call a command on the CODA in start/stop_streaming, we also need
to make sure that a new job doesn't start before the command
finished.
Use a mutex to lock the coda command handling. On timeout, the
device_run job must be marked as finished and the mutex released,
as otherwise coda_release will block.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Kamil Debski <k.debski@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>