USB / PM: Don't try to hide PM QoS flags from usb_port_device_release()

Remove the call to dev_pm_qos_hide_flags(), added by commit 6e30d7c
"usb: Add driver/usb/core/(port.c,hub.h) files", from
usb_port_device_release(), because (1) it is completely unnecessary
(the flags have been removed already by the PM core during the
unregistration of the device object) and (2) it triggers a NULL
pointer dereference in sysfs_find_dirent() (dev->kobj.sd is NULL at
this point).

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/core/port.c

@@ -67,7 +67,6 @@ static void usb_port_device_release(struct device *dev)
 {
 	struct usb_port *port_dev = to_usb_port(dev);
 
-	dev_pm_qos_hide_flags(dev);
 	kfree(port_dev);
 }