leds: Add Dell Business Class Netbook LED driver

This patch adds an LED driver to support the Dell Activity LED on the
Dell Latitude 2100 netbook and future products to come. The Activity LED
is visible externally in the lid so classroom instructors can observe it
from a distance. The driver uses the sysfs led_class and provides a
standard LED interface.

Signed-off by: Bob Rodgers <Robert_Rodgers@dell.com>
Signed-off-by: Louis Davis <Louis_Davis@dell.com>
Signed-off-by: Jim Dailey <Jim_Dailey@dell.com>, Developers
Acked-by: Matthew Garrett <mjg@redhat.com>
Acked-by: Dmitry Torokhov <dtor@mail.ru>
Signed-off-by: Richard Purdie <rpurdie@linux.intel.com>