Add support for National Semiconductor / TI LM3533 lighting power chips.

This is the core driver which provides register access over I2C and
registers the ambient-light-sensor, LED and backlight sub-drivers.
Signed-off-by: NJohan Hovold <jhovold@gmail.com>
Reviewed-by: NMark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: NSamuel Ortiz <sameo@linux.intel.com>