media: videobuf2-core: don't call memop 'finish' when queueing

When a buffer is queued or requeued in vb2_buffer_done, then don't
call the finish memop. In this case the buffer is only returned to vb2,
not to userspace.

Calling 'finish' here will cause an unbalance when the queue is
canceled, since the core will call the same memop again.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>