leds: Add pca9532 led driver

NXP pca9532 is a LED dimmer/controller attached to i2c bus.  It allows
attaching upto 16 leds which can either be on, off or dimmed and/or blinked
with the two PWM modulators available.

This driver is a "new-style" i2c driver that adheres to the driver model and
implements the led framework api.  Since the leds connected to the driver are
platform specific, it is only useful when platform data is passed to the
driver to define what leds are connected to which pins.

Signed-off-by: Riku Voipio <riku.voipio@iki.fi>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Richard Purdie <rpurdie@rpsys.net>