omap3: Fix support for the LEDs connected to GPIO outputs on IGEP v2board

Select CONFIG_LEDS_GPIO to enable IGEP v2 LED support and control of supported
LEDs from userspace. Otherwise GPIO LEDs are exported as GPIO 26, 27 and 28 using
the gpiolib framework.

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