Impact: fix cpumask conversion bug
this warning:
  kernel/sched.c: In function ‘find_busiest_group’:
  kernel/sched.c:3429: warning: passing argument 1 of ‘__first_cpu’ from incompatible pointer type
shows that we forgot to convert a new patch to the new cpumask APIs.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
                *imbalance = min_load_per_task;
                if (sched_mc_power_savings >= POWERSAVINGS_BALANCE_WAKEUP) {
                        cpu_rq(this_cpu)->rd->sched_mc_preferred_wakeup_cpu =
-                                       first_cpu(group_leader->cpumask);
+                               cpumask_first(sched_group_cpus(group_leader));
                }
                return group_min;
        }