[media] stk1160: Make sure current buffer is released

The available (i.e. not used) buffers are returned by stk1160_clear_queue(),
on the stop_streaming() path. However, this is insufficient and the current
buffer must be released as well. Fix it.

Cc: stable@vger.kernel.org
Signed-off-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>