media: amphion: Set video drvdata before register video device

The video drvdata should be set before the video device is registered,
otherwise video_drvdata() may return NULL in the open() file ops, and led
to oops.

Fixes: 3cd08451 ("media: amphion: add vpu v4l2 m2m support")
Cc: <stable@vger.kernel.org>
Signed-off-by: Ming Qian <ming.qian@nxp.com>
Reviewed-by: TaoJiang <tao.jiang_2@nxp.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>