provide disable_cpufreq() function to disable the API.

useful for disabling cpufreq altogether. The cpu frequency
scaling drivers and cpu frequency governors will fail to register.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Dave Jones <davej@redhat.com>
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index 6216115..8ff4427 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -35,6 +35,7 @@
 #ifdef CONFIG_CPU_FREQ
 int cpufreq_register_notifier(struct notifier_block *nb, unsigned int list);
 int cpufreq_unregister_notifier(struct notifier_block *nb, unsigned int list);
+extern void disable_cpufreq(void);
 #else		/* CONFIG_CPU_FREQ */
 static inline int cpufreq_register_notifier(struct notifier_block *nb,
 						unsigned int list)
@@ -46,6 +47,7 @@
 {
 	return 0;
 }
+static inline void disable_cpufreq(void) { }
 #endif		/* CONFIG_CPU_FREQ */
 
 /* if (cpufreq_driver->target) exists, the ->governor decides what frequency