staging: nvec: add LED support

This patch adds support for LEDs connect to a nvec. A single brightness
property is exported to sysfs. LEDs are selected via bitfields in the
brightness value. Also the blinking behavior is selected through this
method. Vendors may use different values for different HW designs.

Signed-off-by: Ilya Petrov <ilya.muromec@gmail.com>
Signed-off-by: Marc Dietrich <marvin24@gmx.de>
[jak@jak-linux.org: Fixed checkpatch warnings]
Signed-off-by: Julian Andres Klode <jak@jak-linux.org>
Acked-by: Marc Dietrich <marvin24@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>