platform/x86: ideapad-laptop: add FnLock LED class device

Some Ideapad/Yoga Laptops have an FnLock LED in the Esc key.

Expose Fnlock as an LED class device for easier OSD support.

Signed-off-by: Gergo Koteles <soyer@irl.hu>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/2db08c948568a8d5352780864956c3271b4e42ce.1712063200.git.soyer@irl.hu


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