usb: gadget: inode.c: fix unbalanced spin_lock in ep0_write

BugLink: http://bugs.launchpad.net/bugs/1724783

commit b7bd98b7 upstream.

Fix bad unlock balance: ep0_write enter with the locks locked from
inode.c:1769, hence it must exit with spinlock held to avoid double
unlock in dev_config.
Signed-off-by: David Eccher <d.eccher@gmail.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

drivers/usb/gadget/legacy/inode.c

@@ -1140,10 +1140,9 @@ ep0_write (struct file *fd, const char __user *buf, size_t len, loff_t *ptr)
 						dev->gadget->ep0, dev->req,
 						GFP_KERNEL);
 				}
+				spin_lock_irq(&dev->lock);
 				if (retval < 0) {
-					spin_lock_irq (&dev->lock);
 					clean_req (dev->gadget->ep0, dev->req);
-					spin_unlock_irq (&dev->lock);
 				} else
 					retval = len;