the ioctl encoder/decoder cmd is under queue lock,
and buf_done is in the irq, it can't be locked with the mutex,
they are not synchronized.
when v4l2_update_last_buf_state is called to
handle the encoder/decoder stop cmd,
the last src buffer may be done at the same time.

so it's possible that last_src_buf is set,
but the output rdy_queue is empty,
then driver won't mark it stopped,
as v4l2_m2m_is_last_draining_src_buf() will always return false and
v4l2_m2m_dst_buf_is_last() return false too.

In this case, the drain will be blocked.

add the hw lock around the ioctl encoder/decoder cmd,
to synchronize with the buf_done.

Fixes: 4911c5ac ("media: imx-jpeg: Implement drain using v4l2-mem2mem helpers")
Signed-off-by: Ming Qian <ming.qian@nxp.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>