sched: remove unused SCHED_INIT_NODE

not used since new numa scheduler init sequence

[James Hogan: see commit cb83b629 (sched/numa: Rewrite the
CONFIG_NUMA sched domain support)]

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: James Hogan <james.hogan@imgtec.com>