HID: wacom: close the wireless receiver on remove()

rmmod/insmod the wacom.ko module does not work for the receiver because
it was not previously closed. Now, we can hack with the wireless receiver
without having to unplug/replug it.

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