HID: hid-oxp: use cancel_delayed_work_sync() in remove

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

HID: hid-oxp: use cancel_delayed_work_sync() in remove

oxp_hid_remove() uses cancel_delayed_work() for all three delayed work
items. cancel_delayed_work() only dequeues a pending work item without
waiting for a currently executing callback to finish. If any of the
work callbacks (oxp_rgb_queue_fn, oxp_btn_queue_fn, oxp_mcu_init_fn) is
running at the time of removal, the callback continues executing
concurrently with hid_hw_close() and hid_hw_stop(), accessing the HID
device after it has been closed and stopped.

Use cancel_delayed_work_sync() instead to ensure that any in-progress
work callback completes before device teardown proceeds.