USB: fix autosuspend when CONFIG_PM isn't set

This patch (as791b) fixes things up to avoid compiler warnings or
errors when CONFIG_USB_SUSPEND or CONFIG_PM isn't set.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
index 239f8e5..e4df9ed 100644
--- a/drivers/usb/core/usb.c
+++ b/drivers/usb/core/usb.c
@@ -214,10 +214,10 @@
 {
 	struct usb_device	*udev = _udev;
 
-	mutex_lock_nested(&udev->pm_mutex, udev->level);
+	usb_pm_lock(udev);
 	udev->auto_pm = 1;
 	usb_suspend_both(udev, PMSG_SUSPEND);
-	mutex_unlock(&udev->pm_mutex);
+	usb_pm_unlock(udev);
 }
 
 #else