None of the code in __qdisc_destroy should be applied to a builtin qdisc
or am I missing something?

The patch below prevents builtin qdiscs from being destroyed and
fixes a refcnt underflow whould lead to a bogus list unlinking
and dev_put.
Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>