HID: lenovo: Add support for ThinkPad X1 Tablet Thin Keyboard Gen2

Add "Thinkpad X1 Tablet Gen 2 Keyboard" PID to hid-lenovo driver to fix trackpoint not working issue.

Signed-off-by: Akira Inoue <niyarium@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.com>