udmabuf: use ENOTTY for invalid ioctls

Reported-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20180911134216.9760-11-kraxel@redhat.com

drivers/dma-buf/udmabuf.c

@@ -260,7 +260,7 @@ static long udmabuf_ioctl(struct file *filp, unsigned int ioctl,
 		ret = udmabuf_ioctl_create_list(filp, arg);
 		break;
 	default:
-		ret = -EINVAL;
+		ret = -ENOTTY;
 		break;
 	}
 	return ret;