PM / devfreq: Remove compiler error after irq.h update

Added <linux/module.h> and <linux/stat.h> to avoid a compiler error
because linux/irq.h no longer includes linux/module.h after Linux 3.2.

Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

drivers/devfreq/devfreq.c

@@ -15,7 +15,9 @@
 #include <linux/errno.h>
 #include <linux/err.h>
 #include <linux/init.h>
+#include <linux/module.h>
 #include <linux/slab.h>
+#include <linux/stat.h>
 #include <linux/opp.h>
 #include <linux/devfreq.h>
 #include <linux/workqueue.h>