ARM: Kirkwood: add modes-map property to ns2-leds nodes

Since the LED modes mapping is no longer hardcoded inside the leds-ns2
driver, then it must be provided through the modes-map property in the
ns2-leds nodes.

Signed-off-by: Vincent Donnefort <vdonnefort@gmail.com>
Acked-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com>