media: tw686x: Fix oops on buffer alloc failure

The error path currently calls tw686x_video_free() which requires
vc->dev to be initialized, causing a NULL dereference on uninitizalized
channels.

Fix this by setting the vc->dev fields for all the channels first.

Fixes: f8afaa8d ("[media] tw686x: Introduce an interface to support multiple DMA modes")
Signed-off-by: Krzysztof Ha?asa <khalasa@piap.pl>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

drivers/media/pci/tw686x/tw686x-video.c

@@ -1190,6 +1190,14 @@ int tw686x_video_init(struct tw686x_dev *dev)
 			return err;
 	}
 
+	/* Initialize vc->dev and vc->ch for the error path */
+	for (ch = 0; ch < max_channels(dev); ch++) {
+		struct tw686x_video_channel *vc = &dev->video_channels[ch];
+
+		vc->dev = dev;
+		vc->ch = ch;
+	}
+
 	for (ch = 0; ch < max_channels(dev); ch++) {
 		struct tw686x_video_channel *vc = &dev->video_channels[ch];
 		struct video_device *vdev;
@@ -1198,9 +1206,6 @@ int tw686x_video_init(struct tw686x_dev *dev)
 		spin_lock_init(&vc->qlock);
 		INIT_LIST_HEAD(&vc->vidq_queued);
 
-		vc->dev = dev;
-		vc->ch = ch;
-
 		/* default settings */
 		err = tw686x_set_standard(vc, V4L2_STD_NTSC);
 		if (err)