ARM: omap2plus_defconfig: Add LP5523 LED driver

The Nokia N900 has an LP5523 driving the RGB LED and the 6 keyboard LEDS.
Enable support for it in omap2plus_defconfig.

Signed-off-by: Sicelo A. Mhlongo <absicsz@gmail.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>