leds: ns2: Absorb platform data

Nothing in the kernel includes the external header
<linux/platform_data/leds-kirkwood-ns2.h> so just push the
contents into the ns2 leds driver. If someone wants to use
platform data or board files to describe this device they
should be able to do so using GPIO machine descriptors but
in any case device tree should be the way forward for these
systems in all cases I can think of, and the driver already
supports that.

Cc: Simon Guinot <simon.guinot@sequanux.org>
Cc: Vincent Donnefort <vdonnefort@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Simon Guinot <simon.guinot@sequanux.org>
Signed-off-by: Pavel Machek <pavel@ucw.cz>