HID: wacom: move down wireless_work()

If wireless_work() wants to reuse parse_and_register(), we need to have
it declared after this function.

No functional changes.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Acked-by: Ping Cheng <pingc@wacom.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>