hwdb: Add mic mute key mapping for HP Elite x360

On the new Elite x360 2 in 1 HP laptops, the microphone mute hotkey is "Fn+F8" and
the scancode for this hotkey is 0x81, but this scancode was mapped to
fn_esc in the HP generic keymap section. To fix this problem, we add
a machine specific keymap section to add the correct keymap rule.

hwdb.d/60-keyboard.hwdb

@@ -651,6 +651,8 @@ evdev:atkbd:dmi:bvn*:bvr*:bd*:svnHewlett-Packard*:pnHPLicrice:*
 # HP EliteBook
 evdev:atkbd:dmi:bvn*:bvr*:bd*:svnHewlett-Packard*:pnHPEliteBook*:*
 evdev:atkbd:dmi:bvn*:bvr*:bd*:svnHP*:pnHPEliteBook*:*
+# HP Elite x360
+evdev:atkbd:dmi:bvn*:bvr*:bd*:svnHP*:pnHPElite*x360*:*
 # HP Elite Dragonfly
 evdev:atkbd:dmi:bvn*:bvr*:bd*:svnHP*:pnHPEliteDragonfly*:*
 # HP ProBook 440 G2