ACPI: asus_acpi: LED display support

This patch adds handling for front LED displays found on W1N and the like.
Additionally, W1N is given its own model_data instance.

Patch originally by Éric Burghard.

Signed-off-by: Karol Kozimor <sziwan@hell.org.pl>
Signed-off-by: Len Brown <len.brown@intel.com>