media: vsp1: Release buffers for each video node

Commit 372b2b03 ("media: v4l: vsp1: Release buffers in
start_streaming error path") introduced a helper to clean up buffers on
error paths, but inadvertently changed the code such that only the
output WPF buffers were cleaned, rather than the video node being
operated on.

Since then vsp1_video_cleanup_pipeline() has grown to perform both video
node cleanup, as well as pipeline cleanup. Split the implementation into
two distinct functions that perform the required work, so that each
video node can release its buffers correctly on streamoff. The pipe
cleanup that was performed in the vsp1_video_stop_streaming() (releasing
the pipe->dl) is moved to the function for clarity.

Fixes: 372b2b03 ("media: v4l: vsp1: Release buffers in start_streaming error path")

Cc: stable@vger.kernel.org # v4.14+
Signed-off-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>