[PKT_SCHED]: Remove unused exports.

This patch removes the following unused EXPORT_SYMBOL's:
- sch_api.c: qdisc_lookup
- sch_generic.c: __netdev_watchdog_up
- sch_generic.c: noop_qdisc_ops
- sch_generic.c: qdisc_alloc

Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: David S. Miller <davem@davemloft.net>