V4L/DVB (5545): Saa7146: Release capture buffers on device close

If the video device (saa7146 on a FF card) was open for capturing,
the close call didn't release the capture buffers.

Signed-off-by: Hartmut Birr <e9hack@gmail.com>
Signed-off-by: Oliver Endriss <o.endriss@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>