sched_ext: Fix use of uninitialized variable in scx_bpf_cpuperf_set()

scx_bpf_cpuperf_set() has a typo where it dereferences the local
variable @sch, instead of the global @scx_root pointer. Fix by
dereferencing the correct variable.

Fixes: 956f2b1 ("sched_ext: Drop kf_cpu_valid()")
Signed-off-by: Andrea Righi <[email protected]>
Reviewed-by: Christian Loehle <[email protected]>
Signed-off-by: Tejun Heo <[email protected]>

Author: arighi

kernel/sched/ext.c

@@ -6401,7 +6401,7 @@ __bpf_kfunc void scx_bpf_cpuperf_set(s32 cpu, u32 perf)
 
 	guard(rcu)();
 
-	sch = rcu_dereference(sch);
+	sch = rcu_dereference(scx_root);
 	if (unlikely(!sch))
 		return;