sched: define and use CPU_PRI_* enums for cpu notifier priorities

Instead of hardcoding priority 10 and 20 in sched and perf, collect
them into CPU_PRI_* enums.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>

include/linux/cpu.h

@@ -48,6 +48,15 @@ extern ssize_t arch_cpu_release(const char *, size_t);
 #endif
 struct notifier_block;
 
+/*
+ * CPU notifier priorities.
+ */
+enum {
+	/* migration should happen before other stuff but after perf */
+	CPU_PRI_PERF		= 20,
+	CPU_PRI_MIGRATION	= 10,
+};
+
 #ifdef CONFIG_SMP
 /* Need to know about CPUs going up/down? */
 #if defined(CONFIG_HOTPLUG_CPU) || !defined(MODULE)