cpuidle: fixup device.h header in cpuidle.h

The "struct device" is only used in sysfs.c.

The other .c files including the private header "cpuidle.h"
do not need to pull the entire headers tree from there as they
don't manipulate the "struct device".

This patch fixes this by moving the header inclusion to sysfs.c
and adding a forward declaration for the struct device.

The number of lines generated by the preprocesor:
Without this patch : 17269 loc
With this patch : 16446 loc

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpuidle/cpuidle.h

@@ -5,8 +5,6 @@
 #ifndef __DRIVER_CPUIDLE_H
 #define __DRIVER_CPUIDLE_H
 
-#include <linux/device.h>
-
 /* For internal use only */
 extern struct cpuidle_governor *cpuidle_curr_governor;
 extern struct list_head cpuidle_governors;
@@ -25,6 +23,9 @@ extern void cpuidle_uninstall_idle_handler(void);
 extern int cpuidle_switch_governor(struct cpuidle_governor *gov);
 
 /* sysfs */
+
+struct device;
+
 extern int cpuidle_add_interface(struct device *dev);
 extern void cpuidle_remove_interface(struct device *dev);
 extern int cpuidle_add_state_sysfs(struct cpuidle_device *device);

drivers/cpuidle/sysfs.c

@@ -12,6 +12,7 @@
 #include <linux/slab.h>
 #include <linux/cpu.h>
 #include <linux/capability.h>
+#include <linux/device.h>
 
 #include "cpuidle.h"