sched: Remove WARN_ON(!sd) from init_sched_groups_power()

sd can't be NULL in init_sched_groups_power() and so checking it for NULL isn't
useful. In case it is required, then also we need to rearrange the code a bit as
we already accessed invalid pointer sd to get sg: sg = sd->groups.
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NPeter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/2bbe633cd74b431c05253a8ce61fdfd5066a531b.1370948150.git.viresh.kumar@linaro.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

kernel/sched/core.c

@@ -5400,7 +5400,7 @@ static void init_sched_groups_power(int cpu, struct sched_domain *sd)
 {
 	struct sched_group *sg = sd->groups;
 
-	WARN_ON(!sd || !sg);
+	WARN_ON(!sg);
 
 	do {
 		sg->group_weight = cpumask_weight(sched_group_cpus(sg));