V4L/DVB: ivtv: Really stop capture on device close

When a capture is started, the firmware also appears to start a secondary
stream. Unless this secondary stream is also stopped, the encoder will remain
active and not reinitialise for the next capture. Unfortunately, setting up
the video source can glitch the encoder and result in undesirable effects that
this initialisation will clear.

Signed-off-by: Ian Armstrong <ian@iarmst.demon.co.uk>
Signed-off-by: Andy Walls <awalls@radix.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>