platform/x86: wmi: Update MAINTAINERS entry

Since 2011, the WMI subsystem is marked as orphaned,
which means that a important part of platform support
for modern notebooks and even desktops is receiving
not enough maintenance.
So i decided to take over the maintenance of the WMI
subsystem.

Signed-off-by: Armin Wolf <W_Armin@gmx.de>
Link: https://lore.kernel.org/r/20231007233933.72121-2-W_Armin@gmx.de
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>