Documentation: syfs-class-firmware-attributes: Lenovo Certificate support

Certificate based authentication is available as an alternative to
password based authentication.

The WMI commands are cryptographically signed using a separate
signing server and will be verified by the BIOS before being
accepted.

This commit details the fields that are needed to support that
implementation. At present the changes are intended for Lenovo
platforms, but have been designed to keep them as flexible as possible
for future implementations from other vendors.

Signed-off-by: Mark Pearson <markpearson@lenovo.com>
Link: https://lore.kernel.org/r/20220317214008.3459-1-markpearson@lenovo.com


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