usb: gadget: lpc32xx_udc: Fix refcount leak in lpc32xx_udc_probe

In the Linux kernel, the following vulnerability has been resolved: usb: gadget: lpc32xx_udc: Fix refcount leak in lpc32xx_udc_probe of_parse_phandle() returns a node pointer with refcount incremented, we should use of_node_put() on it when not need anymore. Add missing of_node_put() to avoid refcount leak. of_node_put() will check NULL pointer.