platform/x86: asus-nb-wmi: Add alternate mapping for KEY_SCREENLOCK

The 0x33 keycode is emitted by Fn + F6 on a ASUS FX705GE laptop.

Reported-by: Nemcev Aleksey <Nemcev_Aleksey@inbox.ru>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20230112181841.84652-1-hdegoede@redhat.com