mfd: Add LM3533 lighting-power core driver

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: Johan Hovold <jhovold@gmail.com>
Reviewed-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>