media: cedrus: Forbid setting new formats on busy queues

Check that our queues are not busy before setting the format or return
EBUSY if that's the case. This ensures that our format can't change
once buffers are allocated for the queue.

Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>