pm_runtime.h: explicitly requires notifier.h

This file was getting notifier.h via device.h --> module.h but
the module.h inclusion is going away, so add notifier.h directly.
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

include/linux/pm_runtime.h

@@ -10,6 +10,7 @@
 #define _LINUX_PM_RUNTIME_H
 
 #include <linux/device.h>
+#include <linux/notifier.h>
 #include <linux/pm.h>
 
 #include <linux/jiffies.h>