Revert "Input: wacom_w8001 - drop use of ABS_MT_TOOL_TYPE"

This reverts commit 5f7e5445

 because
removal of input_mt_report_slot_state() means we no longer generate
tracking IDs for the reported contacts.

Cc: stable@vger.kernel.org
Acked-by: Peter Hutterer <peter.hutterer@who-t.net>
Acked-by: Ping Cheng <pinglinux@gmail.com>