[power] Fix locking in device_{suspend,resume}

We don't need to protect against multiple suspend calls, since subsequent
ones will happen on an empty (or at worst - short) list.

drivers/base/power/resume.c

@@ -31,11 +31,13 @@ int resume_device(struct device * dev)
 /**
  *	device_resume - Restore state of each device in system.
  *
- *	Restore normal device state and release the dpm_sem.
+ *	Walk the dpm_off list, remove each entry, resume the device,
+ *	then add it to the dpm_active list. 
  */
 
 void device_resume(void)
 {
+	down(&dpm_sem);
 	while(!list_empty(&dpm_off)) {
 		struct list_head * entry = dpm_off.next;
 		struct device * dev = to_device(entry);

drivers/base/power/suspend.c

@@ -71,9 +71,6 @@ int suspend_device(struct device * dev, u32 state)
  *	b) prevent other PM operations from happening after we've begun.
  *	c) make sure we're exclusive when we disable interrupts.
  *
- *	device_resume() will release dpm_sem after restoring state to 
- *	all devices (as will this on error). You must call it once you've 
- *	called device_suspend().
  */
 
 int device_suspend(u32 state)
@@ -88,6 +85,7 @@ int device_suspend(u32 state)
 			goto Error;
 	}
  Done:
+	up(&dpm_sem);
 	return error;
  Error:
 	device_resume();