omap3: igepv2: LED gpio-led:green:d1 is active low

Make sure the LED is turned off at boot time, and configure the GPIO LED
device as active low.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Enric Balletbo i Serra <eballetbo@gmail.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>