staging: bcm2835-camera: Ensure all buffers are returned on disable

commit 70ec64cc upstream.

With the recent change to match MMAL and V4L2 buffers there
is a need to wait for all MMAL buffers to be returned during
stop_streaming.

Fixes: 93841670

 ("staging: bcm2835-camera: Remove V4L2/MMAL buffer remapping")
Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.org>
Signed-off-by: Stefan Wahren <wahrenst@gmx.net>
Acked-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Acked-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>