CVE-2024-26715 usb: dwc3: gadget: Fix NULL pointer dereference in dwc3_gadget_suspend

In the Linux kernel, the following vulnerability has been resolved:

usb: dwc3: gadget: Fix NULL pointer dereference in dwc3_gadget_suspend

In current scenario if Plug-out and Plug-In performed continuously
there could be a chance while checking for dwc->gadget_driver in
dwc3_gadget_suspend, a NULL pointer dereference may occur.

Call Stack:

CPU1:                           CPU2:
gadget_unbind_driver            dwc3_suspend_common
dwc3_gadget_stop                dwc3_gadget_suspend
                                    dwc3_disconnect_gadget

CPU1 basically clears the variable and CPU2 checks the variable.
Consider CPU1 is running and right before gadget_driver is cleared
and in parallel CPU2 executes dwc3_gadget_suspend where it finds
dwc->gadget_driver which is not NULL and resumes execution and then
CPU1 completes execution. CPU2 executes dwc3_disconnect_gadget where
it checks dwc->gadget_driver is already NULL because of which the
NULL pointer deference occur.