media: uvcvideo: Fix sequence number when no EOF

media: uvcvideo: Fix sequence number when no EOF

If the driver could not detect the EOF, the sequence number is increased
twice:
 1) When we enter uvc_video_decode_start() with the old buffer and FID has
   flipped => We return -EAGAIN and last_fid is not flipped
 2) When we enter uvc_video_decode_start() with the new buffer.

Fix this issue by moving the new frame detection logic earlier in
uvc_video_decode_start().

This also has some nice side affects:

- The error status from the new packet will no longer get propagated
  to the previous frame-buffer.
- uvc_video_clock_decode() will no longer update the previous frame
  buf->stf with info from the new packet.
- uvc_video_clock_decode() and uvc_video_stats_decode() will no longer
  get called twice for the same packet.

Cc: stable@kernel.org
Fixes: 650b95feee35 ("[media] uvcvideo: Generate discontinuous sequence numbers when frames are lost")
Reported-by: Hans de Goede <hansg@kernel.org>
Closes: https://lore.kernel.org/linux-media/CANiDSCuj4cPuB5_v2xyvAagA5FjoN8V5scXiFFOeD3aKDMqkCg@mail.gmail.com/T/#me39fb134e8c2c085567a31548c3403eb639625e4
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Hans de Goede <johannes.goede@oss.qualcomm.com>
Signed-off-by: Hans de Goede <johannes.goede@oss.qualcomm.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>