media: amphion: reinit vpu if reqbufs output 0

according to v4l2 stateful decoder document 4.5.1.3. State Machine,
the state should change from seek to initialization
if call VIDIOC_REQBUFS(OUTPUT, 0).

so reinit the vpu decoder if reqbufs output 0

Fixes: 6de8d628

 ("media: amphion: add v4l2 m2m vpu decoder stateful driver")
Signed-off-by: Ming Qian <ming.qian@nxp.com>
Tested-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Reviewed-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>