platform/x86: asus-wmi: add WMI method to show if egpu connected

Exposes the WMI method which tells if the eGPU is properly connected
on the devices that support it.

Signed-off-by: Luke D. Jones <luke@ljones.dev>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20230630053552.976579-5-luke@ljones.dev


Signed-off-by: Hans de Goede <hdegoede@redhat.com>