[PATCH to drm/nouveau] nouveau: Mark nouveau subchannel unbound nouveau_grobj_free

[Maarten Lankhorst <m.b.lankhorst-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

Valgrind throws warns about a user-after-free if you try to bind a
new subchannel after the old one in that slot was freed,
so remove it from the channel list.

Signed-off-by: Maarten Lankhorst <m.b.lankhorst-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>

--- a/nouveau/nouveau_grobj.c
+++ b/nouveau/nouveau_grobj.c
@@ -100,12 +99,13 @@ nouveau_grobj_free(struct nouveau_grobj **grobj)
 		struct drm_nouveau_gpuobj_free f;
 
 		FIRE_RING(&chan->base);
-
 		f.channel = chan->drm.channel;
 		f.handle  = nvgrobj->base.handle;
 		drmCommandWrite(nvdev->fd, DRM_NOUVEAU_GPUOBJ_FREE,
 				&f, sizeof(f));	
 	}
+	if (nvgrobj->base.bound != NOUVEAU_GROBJ_UNBOUND)
+		chan->base.subc[nvgrobj->base.subc].gr = NULL;
 	free(nvgrobj);
 }