media: cedrus: drop min_buffers_needed.

There is no reason for the cedrus driver to set min_buffers_needed.
A non-zero min_buffers_needed can cause problems with the Request API
if start_streaming fails when queueing a buffer from a request.

Since it is not needed for this driver, just remove it.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Cc: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Reviewed-by: Ezequiel Garcia <ezequiel@collabora.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>