Micmute Key support of ThinkCentre M820z and M920z (systemd#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 systemd#9619,
We better combine M800z and M820/M920z entries and use the "evdev" prefix.

hwdb/60-keyboard.hwdb

@@ -756,9 +756,9 @@ evdev:atkbd:dmi:bvn*:bvr*:svnLENOVO*:pn*IdeaPad*Z370*:pvr*
 evdev:atkbd:dmi:bvn*:bvr*:bd*:svnLENOVO*:pn*Lenovo*V480*:pvr*
  KEYBOARD_KEY_f1=f21
 
-# Lenovo Thinkcentre M800z AIO machine
+# Lenovo ThinkCentre M800z/M820z/M920z AIO machines
 # key_scancode 00 is KEY_MICMUTE
-keyboard:name:Microphone Mute Button:dmi:bvn*:bvr*:bd*:svnLENOVO*:pn*
+evdev:name:Microphone Mute Button:dmi:bvn*:bvr*:bd*:svnLENOVO*:pn*
  KEYBOARD_KEY_00=f20
 
 # enhanced USB keyboard