platform/x86: wmi: Remove chardev interface

The design of the WMI chardev interface is broken:
- it assumes that WMI drivers are not instantiated twice
- it offers next to no abstractions, the WMI driver gets
a raw byte buffer
- it is only used by a single driver, something which is
unlikely to change

Since the only user (dell-smbios-wmi) has been migrated
to his own ioctl interface, remove it.

Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Armin Wolf <W_Armin@gmx.de>
Link: https://lore.kernel.org/r/20231210202443.646427-6-W_Armin@gmx.de


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