omap3: fix and improve the LED handling on IGEP v2 board

The IGEP v2 board has four leds, this patch allows control all
of these LEDs using the LED class if CONFIG_LEDS_GPIO is selected
or using the General Purpose Input/Output (GPIO) interface if
CONFIG_LEDS_GPIO is not selected.

Signed-off-by: Enric Balletbo i Serra <eballetbo@gmail.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>