platform/x86: hp-wmi: add micmute to hp_wmi_keymap struct

Fixes micmute key of HP Envy X360 ey0xxx.

Signed-off-by: Fae <faenkhauser@gmail.com>
Link: https://lore.kernel.org/r/20230425063644.11828-1-faenkhauser@gmail.com
Cc: stable@vger.kernel.org
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>