usb: gadget: pch_udc: Fix disconnect issue

ISSUE:
When the driver notifies a gadget of a disconnect event, a system
rarely freezes.

CAUSE:
When the driver calls dev->driver->disconnect(), it is not calling
spin_unlock().
Signed-off-by: Tomoya MORINAGA <tomoya.rohm@gmail.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/gadget/pch_udc.c

@@ -2335,8 +2335,11 @@ static void pch_udc_svc_ur_interrupt(struct pch_udc_dev *dev)
 		/* Complete request queue */
 		empty_req_queue(ep);
 	}
-	if (dev->driver && dev->driver->disconnect)
+	if (dev->driver && dev->driver->disconnect) {
+		spin_unlock(&dev->lock);
 		dev->driver->disconnect(&dev->gadget);
+		spin_lock(&dev->lock);
+	}
 }
 
 /**