Thinkpad X200 volume hotkeys

[Andreas Hecht <a.e.hecht%t-online.de@localhost>]

I am trying to get the volume hotkeys (VolumeUp, VolumeDown, VolumeMute) on my
Lenovo Thinkpad X200 to work. Unfortunately the respective hotkey events are
not seen by thinkpad_acpi driver's thinkpad_notify_handler. The comments (->
"Not seen on T61") in the driver indicate that these volume hotkeys are not
working for the Thinkpad T61 either. Could someone please point me in the right
direction how to fix this? The volume hotkeys work fine on the same X200 with
OpenBSD 7.4.

-Andreas