HID: wacom: break out wacom_intuos_get_tool_type

Allow to reuse the code in a later series and simplifies
the reading of wacom_intuos_inout().

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