PM: Remove unbalanced mutex_unlock() from dpm_resume()

Remove an unnecessary unlocking of dpm_list_mtx in the error path
in drivers/base/power/main.c:dpm_suspend() .
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/base/power/main.c

@@ -479,7 +479,6 @@ static int dpm_suspend(pm_message_t state)
 			mutex_lock(&dpm_list_mtx);
 			if (list_empty(&dev->power.entry))
 				list_add(&dev->power.entry, &dpm_locked);
-			mutex_unlock(&dpm_list_mtx);
 			break;
 		}
 		mutex_lock(&dpm_list_mtx);