V4L/DVB (8682): V4L: fix return value of register video func

If a wrong device type is used with video_register_device_index() it should
better return an error number, instead of a constant.
Signed-off-by: Henrik Kretzschmar <henne@nachtwindheim.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>

drivers/media/video/v4l2-dev.c

@@ -281,7 +281,7 @@ int video_register_device_index(struct video_device *vfd, int type, int nr,
 	default:
 		printk(KERN_ERR "%s called with unknown type: %d\n",
 		       __func__, type);
-		return -1;
+		return -EINVAL;
 	}
 
 	/* pick a minor number */