net_sched: sfq: remove unused macro

not used anymore since ddecf0f4
(net_sched: sfq: add optional RED on top of SFQ).

Signed-off-by: Florian Westphal <fw@strlen.de>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>