1. Add support for initializing onboard LEDs based on board definition. Maximum LED count has been set to 12. 2. Introduce mraa_led_init_raw API for initializing LEDs based on function name. This API can be used by platforms which doesn't have mapping in board definition. Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>