The type is never set but we check for it in wacom_wireless_irq().
It looks like this is a big hack from the beginning, so fill in the gap
only.

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