sched: Remove unused function group_first_cpu()

As of commit afe06efd ("sched: Extend scheduler's asym packing")
group_first_cpu() became an unused function, remove it.
Signed-off-by: Zhang Qiao <zhangqiao22@huawei.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Link: https://lore.kernel.org/r/20220617181151.29980-3-zhangqiao22@huawei.com

kernel/sched/sched.h

@@ -1810,15 +1810,6 @@ static inline struct cpumask *group_balance_mask(struct sched_group *sg)
 	return to_cpumask(sg->sgc->cpumask);
 }
 
-/**
- * group_first_cpu - Returns the first CPU in the cpumask of a sched_group.
- * @group: The group whose first CPU is to be returned.
- */
-static inline unsigned int group_first_cpu(struct sched_group *group)
-{
-	return cpumask_first(sched_group_span(group));
-}
-
 extern int group_balance_cpu(struct sched_group *sg);
 
 #ifdef CONFIG_SCHED_DEBUG