HID: wacom: Add new Intuos Pro Small (PTH-460) device IDs

Add the new PIDs to wacom_wac.c to support the new model in the Intuos Pro series.

Signed-off-by: Ping Cheng <ping.cheng@wacom.com>
Tested-by: Aaron Armstrong Skomra <aaron.skomra@wacom.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>