ACPI: Allow a WAN module enable/disable on a Thinkpad X60.

The WAN (Sierra Wireless EV-DO) module is very similar to the
Bluetooth module.  It appears on the USB bus when enabled.  It can be
controlled via hot key, or directly via ACPI.  This change enables
direct control via ACPI.

I have tested it on my Lenovo Thinkpad X60; I guess it will probably
work on other Thinkpad models which come with this module installed.

Signed-off-by: Jeremy Fitzhardinge <jeremy@goop.org>
Ack'd by: Borislav Deianov <borislav@users.sf.net>
Signed-off-by: Len Brown <len.brown@intel.com>