USB: testing driver: don't free a locked mutex

Dopey thing to do and lockdep will (or should) warn.

Spotted by Daniel Walker.

Cc: Matthias Kaehlcke <matthias.kaehlcke@gmail.com>
Cc: Daniel Walker <dwalker@mvista.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

drivers/usb/misc/usbtest.c

@@ -1992,8 +1992,6 @@ static void usbtest_disconnect (struct usb_interface *intf)
 {
 	struct usbtest_dev	*dev = usb_get_intfdata (intf);
 
-	mutex_lock(&dev->lock);
-
 	usb_set_intfdata (intf, NULL);
 	dev_dbg (&intf->dev, "disconnect\n");
 	kfree (dev);