HID: asus: refactor the two workqueues and init sequence

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

HID: asus: refactor the two workqueues and init sequence

Multiple issues have been found within the hid-asus driver:
- unchecked size in asus_raw_event()
- unclean teardown of asus_probe on failure
- possible use-after-free in asus_probe
- multiple workqueue used for jobs where one was enough
- sleeping calls in atomic context
- packets of incorrect size being sent to the keyboard controller

Join the two workqueues into one reusing the stopping mechanism
of the brightness workqueue, use the joined workqueue to also
move the asus_wmi_send_event() sleeping call away from atomic
context and add a size check in asus_raw_event().