Add LED support for AR5BXB6 IBM Thinkpad PCIe adapters

Add LED support on the IBM ThinkPad 11a/b/g Wireless LAN Mini Express
Adapter (AR5BXB6), found on the IBM/Lenovo Thinkpad X60/T60/Z60 series.

Signed-off-by: Paride Legovini <legovini@spiro.fisica.unipd.it>
Signed-off-by: Bob Copeland <me@bobcopeland.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>