HID: wacom: Add 2nd gen Intuos Pro Small support

The existing INTUOSP2_BT device class supports LEDs and this device
does not. A new device class enum entry, "INTUOSP2S_BT", is created
to avoid the INTUOSP2_BT LED code.

Signed-off-by: Aaron Armstrong Skomra <aaron.skomra@wacom.com>
Reviewed-by: Jason Gerecke <jason.gerecke@wacom.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>