HID: hid-lenovo-go: cancel cfg_setup work in hid_go_cfg_remove()

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

HID: hid-lenovo-go: cancel cfg_setup work in hid_go_cfg_remove()

hid_go_cfg_probe() initialises drvdata.go_cfg_setup and schedules it
to run 2 ms later:

INIT_DELAYED_WORK(&drvdata.go_cfg_setup, &cfg_setup);
schedule_delayed_work(&drvdata.go_cfg_setup, msecs_to_jiffies(2));

cfg_setup() dereferences drvdata.hdev to issue MCU command requests.
hid_go_cfg_remove() tears down sysfs and stops the HID device, but
never drains the delayed work. If the device is unbound within the
2 ms scheduling delay (a probe failure rolling back via remove, or a
fast rmmod after probe), the work fires after hid_destroy_device()
has dropped its reference and released the underlying hdev struct,
leaving cfg_setup() with a stale drvdata.hdev pointer.

Mirror the sibling driver hid-lenovo-go-s.c, whose hid_gos_cfg_remove()
already calls cancel_delayed_work_sync() on its analogous work, and
drain go_cfg_setup at the top of hid_go_cfg_remove(). The cancel
must come before guard(mutex)(&drvdata.cfg_mutex) because cfg_setup()
acquires that mutex; reversing the order would deadlock.