CVE-2023-53356 usb: gadget: u_serial: Add null pointer check in gserial_suspend

In the Linux kernel, the following vulnerability has been resolved: usb: gadget: userial: Add null pointer check in gserialsuspend Consider a case where gserialdisconnect has already cleared gser-ioport. And if gserialsuspend gets called afterwards, it will lead to accessing of gser-ioport and th...