When Fn-Esc is pressed on the keyboard, it emits the scancode which could
be used to sync the fn_lock sysfs state.

Previously fn_lock only allowed to set new Fn-lock state and did not
keep the value in sync upon Fn-Esc press, which is now fixed.
Signed-off-by: Florian Klink <flokli@flokli.de>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>