[media] coda: issue seq_end_work during stop_streaming

This patch queues seq_end_work and flushes the queue during stop_streaming
and clears the ctx->initialized flag. This allows to start streaming again
after stopping streaming without releasing the context.

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@osg.samsung.com>