Micmute Key support of ThinkCentre M820z and M920z (#9619)

Micmute Key support of ThinkCentre M820z and M920z (#9619)

Micmute Key support of ThinkCentre M820z and M920z

There was a ThinkCentre M800z Micmute Key support entry.
But on new models M820z and M920z, the lines must change a bit,
the keyboard:name... must change to evdev:name.
Already tested on the M820z and M920z hardwares.

Per Poettering's comment in https://github.com/systemd/systemd/pull/9619,
We better combine M800z and M820/M920z entries and use the "evdev" prefix.