sched: Fix compile error for UP,!NOHZ

Commit 69e1e811 ("sched, nohz: Track nr_busy_cpus in the
sched_group_power") messed up the static inline function definition.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>
Link: http://lkml.kernel.org/n/tip-abjah8ctq5qrjjtdiabe8lph@git.kernel.orgSigned-off-by: Ingo Molnar <mingo@elte.hu>

include/linux/sched.h

@@ -277,7 +277,7 @@ extern void set_cpu_sd_state_idle(void);
 extern int get_nohz_timer_target(void);
 #else
 static inline void select_nohz_load_balancer(int stop_tick) { }
-static inline void set_cpu_sd_state_idle(void);
+static inline void set_cpu_sd_state_idle(void) { }
 #endif
 
 /*