media: camss: Clean up received buffers on failed start of streaming

It is required to return the received buffers, if streaming can not be
started. For instance media_pipeline_start() may fail with EPIPE, if
a link validation between entities is not passed, and in such a case
a user gets a kernel warning:

  WARNING: CPU: 1 PID: 520 at drivers/media/common/videobuf2/videobuf2-core.c:1592 vb2_start_streaming+0xec/0x160
  <snip>
  Call trace:
   vb2_start_streaming+0xec/0x160
   vb2_core_streamon+0x9c/0x1a0
   vb2_ioctl_streamon+0x68/0xbc
   v4l_streamon+0x30/0x3c
   __video_do_ioctl+0x184/0x3e0
   video_usercopy+0x37c/0x7b0
   video_ioctl2+0x24/0x40
   v4l2_ioctl+0x4c/0x70

The fix is to correct the error path in video_start_streaming() of camss.

Fixes: 0ac2586c ("media: camss: Add files which handle the video device nodes")
Signed-off-by: Vladimir Zapolskiy <vladimir.zapolskiy@linaro.org>
Reviewed-by: Robert Foss <robert.foss@linaro.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

drivers/media/platform/qcom/camss/camss-video.c

@@ -495,7 +495,7 @@ static int video_start_streaming(struct vb2_queue *q, unsigned int count)
 
 	ret = video_device_pipeline_start(vdev, &video->pipe);
 	if (ret < 0)
-		return ret;
+		goto flush_buffers;
 
 	ret = video_check_format(video);
 	if (ret < 0)
@@ -524,6 +524,7 @@ static int video_start_streaming(struct vb2_queue *q, unsigned int count)
 error:
 	video_device_pipeline_stop(vdev);
 
+flush_buffers:
 	video->ops->flush_buffers(video, VB2_BUF_STATE_QUEUED);
 
 	return ret;